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Rising Tide

Seen from space, California's coast is a thin white line between the deep blue ocean and the green and brown of a seasonally arid land. In a thousand miles of pounding surf and steep cliffs, only once does the ocean enter deeply into the land. Three great, kidney-shaped bays spread inland and eastward from the ocean, meeting ribbons of water draining snow-capped mountains to the east. The three shallow bodies together form San Francisco Bay, arm of the sea and estuary of the Sacramento and San Joaquin Rivers. From about five miles up-the altitude of a commercial airliner-cities, highways, and farmland come into view. They suggest the widespread presence and influence of human beings on the landscape of the San Francisco Bay Area. Seen from a descending airplane or the mountaintops that ring the bay, the baylands come into focus. At low tide, dark brown mudflats and shallow channels dominate much of the bay surface. A swath of green salt marsh and bulrushes covers the shores of the northern bays, and the ridgetops around the bay are open grassland parks. From this height, a human landscape dominates the bayshore. Cities, suburbs, airports, vast seaport shipping facilities, industrial areas, garbage dumps, salt ponds, and diked farmland extend to the horizon. But from water level, the cities recede and the bay is revealed as an enormous open space largely free of human constructions. If our camera eye drops still lower, beneath the surface of the turbid water, we can see that the foundation of this human landscape is the thick mud of the bay bottom. The cities, the airports, and the farmland all rest on a drowned river valley's silts.

Our descent from the stratosphere to the bay floor reveals a unique natural feature: the only major break in the Pacific coastal wall between Mexico and the Columbia River. This is western North America's most important estuary. Forty percent of the rain and snow that falls on California drains through this estuary into the ocean. Winds blow through the narrow gap in the rampart of the coastal mountains, cooling the interior valleys and producing unique microclimates, fog belts, and windswept hilltops. Water also flows through the gap. Twice each day, the ocean's great tides, heaving up and down in response to the pull of the sun and moon, sweep up into the interior of California and then, with power greater than any river, rush out again. As the tides move through the bays, they mix cold, salty ocean water with warmer, fresh river water. Swirling sediment-laden currents carry this nutrient-rich brew back and forth, upstream and down under the California sunshine, gradually but inexorably toward the sea.

This richness is the product of enormous and ongoing geological change. San Francisco Bay as we know it is a recent and ephemeral phenomenon. The water's edge today laps against a shoreline dozens of feet higher than when human beings first entered the region. At the height of the last ice age, approximately twenty thousand years ago, so much of the earth's water was locked into miles-high glaciers that the ocean beaches lay beyond what are now the Farallon Islands, more than thirty miles from the Golden Gate. About ten thousand years ago the rising sea first pushed through the Golden Gate into the river valleys beyond. For more than five millennia the water swallowed the land and created San Francisco Bay.

San Francisco Bay, then, is a very recent landform. Geologists tell us that the bay's presence is cyclical. During the ice ages, the ocean retreats offshore. And during the interglacial periods-warming periods like the one we are in now-a bay briefly appears. Sea levels have reached present heights only once before, and rarely have they been high enough to come through the Golden Gate at all. The bay we have now is the largest and longest lasting in all of human history. We live at a time of unusually high water, near the top of the tide.

Life on earth ultimately takes its energy from the sun. But sunshine alone does not guarantee life, as any visitor to the desert knows. More than four-fifths of the surface of the earth is open ocean, desert, and ice. These are sunny places. Yet the open oceans, deserts, and polar ice caps are among the most barren habitats on earth. For plants to grow, they must have sufficient moisture as well as light. All celled creatures depend on a handful of key chemicals that are found on the continents. These nutrients are constantly washing away into the sea. The continents are nutritionally poor, and they get poorer all the time. The sea, on the other hand, is too diffuse. The great stocks of minerals eroded from the land are dissipated in the immense volume of seawater covering two-thirds of the planet. Life is most abundant when limiting chemicals-particularly nitrogen and phosphorus-occur in the presence of plentiful sunshine and water. This happens most often on the edges between land and water. And it happens most effectively where rivers carrying their precious cargo of eroded terrestrial nutrients meet the sea. At these estuaries, freshwater and salt water mingle, and rivers drop their loads of rich silt and sand. Thanks to this unique combination of light, nutrients, and topography, as geologist and marsh scholar Nathaniel Shaler observed more than a century ago, "the undersea portion of the beach becomes, of all the water-covered areas, the fittest seat for life." Shaler referred to the tide-washed shoreline. Around the edges of the estuary, shallow-water communities of plants take up the nutrients from the fertile sediments. These marshes are the tidelands, the area of land and water existing between high and low tide.

Life moves with the water. Microscopic plants travel in the water column, blooming in the nutrient-rich, sun-soaked shallows. Diatoms encrusted on flecks of mud and free-floating plankton alike capture the energy of the sun and make it available for creatures small and large. This productivity is concentrated on the edge of the bay. On the margin, salt-tolerant marsh grasses colonize soft mud. The partially submerged grasses break up the tidal currents and shelter myriad creatures. Young salmon come downstream and use the salt marshes and shallows as rearing areas. The young fish grow quickly in these sheltered puberty pools. Crabs and other ocean species move into the brackish bay to mate, giving their young the benefit of the nutrient-rich estuary and its protection. Terrestrial animals feed on the plants and fish in the marshes. Human beings, terrestrial animals ourselves, rely on the estuary's fertility and productivity in many ways, but most directly for the shallow water fisheries. Historically, California's most consistent and most valuable fish species were found in San Francisco Bay.

All of this spectacular richness rests on something quite prosaic. Rivers and streams carry nutrients into San Francisco Bay, and the tides recirculate them. A speck of silt entering the bay from the delta does not continue onward, in stately fashion, to the ocean. The tides, pushing and pulling the bay's water in currents more powerful than any river on earth, carry every cup of river water back and forth from delta to deep bay, up and down in the water column. Between the moment that a drop of muddy water enters Suisun Bay and the instant that it finally leaves the bay for the Pacific Ocean, it may whirl hundreds of miles through the bays and delta. The tides recirculate the water twice daily. This mixing is the key to the bay's fecundity. Thanks to the tides, bay marshlands receive a constant flow of nutrients. The tidal plants never lack, because the bay brings more with every tide.

San Francisco Bay's tidal wetlands, like tide marshes worldwide, are extraordinarily productive of vegetation. According to scientists, the largest "above-ground standing crop in North America" may belong to bulrushes in the freshwater tidelands of the Sacramento-San Joaquin delta. Growing nine to twelve feet in a year, these rushes annually produce over half a pound of plant matter per square foot, a density nearly unparalleled in nature. Because of the rivers and tides, this amazing richness is not trapped in place. Tiny pieces of plant stems break off and are circulated by the tides. The delta's freshwater tidelands, together with the salt marshes fringing the bays, annually contribute 2.2 billion pounds of fixed carbon to the San Francisco Bay estuary. Carbon compounds are the building blocks of all life on earth. Dissolved in water or mixed in the atmosphere as carbon dioxide gas, available carbon measures how much plant growth can occur. It is a measure of productivity.

Not even modern agriculture, assisted by fertilizers and machinery, can match the output of salt marshes. Tidal wetlands exist at the bottom of rivers and top of the ocean, where they build up from fertile soil washed off the land by rainfall. They are sustained by the constant push and pull of the tide, which brings in nutrients and animals and carries away waste. Acre for acre, tidal wetlands convert more sunlight, air, and water to plant matter and animal flesh than any grassland or tropical rain forest. Salt marshes are nature's furnaces, stoking a rich food web that sustains biological communities all over the world.

Despite all this movement, the communities of the tidal margin are relatively stable compared to those of central California's upland habitats. Climate cycles made the valleys and hills sometimes very fecund, but these areas were also prone to extended drought. The bayshore, on the other hand, could be depended upon for food resources during all seasons and in all years. The marshes and shellfish beds did not dry up, burn down, or wash away; they were rare reliable food sources in a feast-or-famine landscape. As a result, these were the places where California's native peoples congregated.

A Crowded and Cultivated Land

In 1793, His Britannic Majesty's captain George Vancouver crept into San Francisco Bay in command of a small flotilla of vessels. Entering the territory of a traditional enemy without permission, Vancouver was relieved to discover that the Spanish fort commanding the imposing south shore of the bay entrance, the Presidio de San Francisco, was defended by only a small band of troops manning a handful of decrepit cannons. After a tense exchange of formal greetings with the Presidio's proud but outgunned commander, Vancouver went ashore with his ship's surgeon, naturalist Archibald Menzies. Menzies was eager to compare the plants and animals of this unknown coast to his collections from elsewhere in the north Pacific, but he contented himself with exploring the long lagoon behind the sandy beach near the Presidio. Vancouver, meanwhile, began a busy round of social activities and surreptitious spying. He dined with the officers of the Presidio, ogled their wives and daughters, and visited the nearby Mission San Francisco. Vancouver and his lieutenants borrowed horses from their hosts to visit Mission Santa Clara at the south end of the bay. The party picnicked in a grove of oaks that reminded Vancouver of an English park. Surveying the brown autumn hills and plains, dotted with majestic oaks and occasional streams, the Englishman saw a landscape that recalled familiar European places, and that seemed equally imbued with promise. But, Vancouver judged, the Spanish were neglecting this potential. After a quarter century of Spanish religious instruction and economic guidance, the Indians, the laborers of the region, "still remained in the most abject state of uncivilization." Only the introduction of "foreign commercial intercourse" could "stimulate the Indians to industry," asserted Vancouver.

Neither Vancouver nor his lieutenants recognized that human hands had already shaped the shores of San Francisco Bay. Archibald Menzies was a professional naturalist and a keen observer of Pacific coastal habitats whose name graces many of the region's plant species, including the most common conifer of the coast, the Douglas fir, Pseudotsuga menziesii. Yet Menzies had little to say about the salt marshes and shoreline plants of San Francisco Bay. Partly this was due to his unfortunate timing. November is among the least rewarding times to see San Francisco Bay's rich diversity of flowering plants. And the salt marshes, in any case, are not laden with bright flowers. Their beauty is found more in shades of green, grey, and brown: the sort of beauty revealed by winter, a beauty of the bone. Menzies's eye wandered past the salt marsh and up toward the brown hills, which he so badly wanted to see in bloom. Like other nineteenth-century European visitors to San Francisco Bay, Vancouver and Menzies hardly noticed the marshes lining its shore. These men saw the bay as a world apart from the land, and it was the land that interested them for its potential agricultural bounty.

When we read Menzies's, Vancouver's, and other Europeans' descriptions of San Francisco Bay, we can be fooled, as they were, into thinking that neither Ohlones nor the Spanish and Mexicans who lived among them manipulated their natural surroundings. It would be a grave mistake to repeat this error. The Indians and Spanish did change the landscape, just not in the ways that English visitors expected. In recent years, a group of historical ecologists has shown that San Francisco Bay's tidal margin contained a remarkable diversity of habitats ranging across a spectrum from salty and marine to freshwater and terrestrial. Many of these habitats were made or maintained by human beings. The bunchgrass prairies and parklike oak savannahs, for instance, that so captivated Vancouver's men on their ride to Mission Santa Clara, would have been overgrown by brush without frequent fires set by Indians. Ohlones maintained these grassy plains with their widely spaced majestic oaks. Native peoples surely also modified tidal and aquatic habitats. Like other coastal peoples of the Pacific, Ohlones used the shoreline intensively. They harvested fish, shellfish, and other food resources from the marshes and bay waters. They built fish traps and shot and netted waterfowl. Historians and ecologists have also speculated that native peoples enhanced naturally occurring salt evaporation ponds to improve their harvests of the precious mineral, which they traded with inland peoples. Ohlone oral tradition recalls some of these practices and their purposes in a social world whose heart was the water's edge.

A Landscape of Shellmounds

California's first humans arrived during the final millennia of the last ice age. They probably came by water. The oldest archaeological sites are from islands off the central California coast and from inland sites not far from the coast. It is very likely that people lived in the river valleys before San Francisco Bay covered them. Their campsites, their villages, and their burials are now themselves buried by thousands of years of tides and silt. What is certain is that the bayshore has been home to thousands of people for thousands of years. As late as the twentieth century, hundreds of mounds dotted the bay's edge.

Much of what modern scholars know about San Francisco Bay's native peoples derives from the waste they left behind. Native peoples built hundreds of mounds around San Francisco Bay from the shells of mollusks they collected from the bayshore. These mounds, which ranged in size from a few yards to dozens of yards in diameter, were more than just middens, or kitchen garbage. Most of the few large mounds excavated contained human remains buried in ritual fashion, and they clearly served multiple purposes for the peoples who built them over long centuries. Archaeologists excavating the shellmounds have constructed a cultural history of human use of the bayshore for at least three millennia and thousands of years longer farther inland. As Joe Eaton notes, "There are places in California with the time-depth of Troy or Jericho." Scholars can only speculate on how such intensive harvest may have influenced favored shellfish species, but it is clear that Indian people were huge consumers of marsh and mudflat animals.

The Ohlone economy was local, personal, knowledgeable, and communal. It was part of a flexible economy adapted to unpredictable cycles of rain and drought. These were people who knew intimately the productive places and seasons of the baylands. Native peoples harvested so many shellfish that they built hundreds of huge mounds around the bay. In 1906, University of California scholar N. C. Nelson found that, despite decades of destruction by farmers and road builders, several hundred mounds still remained. The shellmounds held deep cultural meaning for Ohlone people. Some mounds held hundreds of burials, with bodies carefully oriented and accompanied by special objects. It is one of the great tragedies of California history that so much of the meaning of these spaces has been lost. Yet even stripped of their context the shellmounds are testimony to the tremendous productivity of the tidelands and their central place in the indigenous economy. Far from subsisting solely on the acorn, deer, and salmon that anthropologists once assumed were the basis of all California native economies, Ohlones used resources from every part of their landscape, from peaks to bay. At the center of their lives lay the bay's edge. As Europeans colonized California, they destroyed native economies by limiting Indian access to the most important resources, which lay along the bayshore.

War and epidemic disease broke the back of independent Ohlone communities in the decades after the Spanish arrived in the bay region. Shattered by sickness and warfare, and perhaps attracted by the material wealth and spiritual power of the Spanish god, Indian villages surrounding the bay broke up and their members joined the Franciscan missions. All over California, missions absorbed Indian communities, but nowhere more so than in the San Francisco Bay region. Between 1776 and 1820 Spanish missionaries constructed five missions to serve the dense native population around San Francisco Bay. By 1821, missionaries had successfully removed native peoples from their villages and family groups along the entire coast from San Diego to San Francisco. These people were reconfigured as members of mission communities, where their identity was based on labor. Indian workers made a wide range of products for local use and sale, from soap to wine to pottery; they managed mission gardens, planted and harvested mission fields of wheat, and oversaw mission livestock herds that totaled nearly four hundred thousand cattle, sixty thousand horses, and over three hundred thousand pigs, sheep, and goats. This new wealth came at a tremendous cost. California's indigenous population had once been among the highest in North America. During the fifty years between the founding of missions in Alta California and the end of Spanish rule in 1821, the missions buried tens of thousands of acolytes. The province's native population fell by 75 percent, from about seventy-two thousand to eighteen thousand.

Mission life was brutal, and where possible, native people rebelled. Spanish military power, concentrated along the bay shoreline and directed against tightly controlled, linguistically divided Indian populations, meant that outright armed resistance was never successful in San Francisco Bay missions. Native peoples more commonly ran away, returning to family groups. Yet ethnic divisions between native groups at the missions made even escape difficult, as a visitor observed at Mission San Jose in 1806: "Every now and then attempts at escape are made. On such occasions, no sooner is any one missed than search is made after him; and as it is always known to what tribe the fugitive belongs, and on account of the enmity which subsists among the different tribes, he can never take refuge in any other (a circumstance which perhaps he scarcely thought of beforehand), it is scarcely possible for him to evade the searches of those who are sent in pursuit of him."

After the 1790s, as independent Indian communities disappeared from the area immediately surrounding the bay, runaways fled farther east into the marshes and grasslands of the San Joaquin valley. Here mission runaways joined other tribes, such as the Yokuts, or created new communities based on raiding and rustling mission stock. Spanish and later Mexican military expeditions crushed these runaway communities when they could find them. In 1828, hundreds of mission runaways founded a fortified village in the San Joaquin valley, from which they carried out raids against mission herds. A series of Mexican military expeditions against the rebels, who were led by a Mission San Jose acolyte called Estanislao, eventually forced the runaways back into the missions. But runaways and valley Indians so frequently raided mission herds that mission livestock numbers actually declined during the nineteenth century despite the great expansion of ranches into Indian lands. California's native peoples, like those of other North American borderlands, responded and adapted as best they could to the triple whammy of European invasion, epidemic disease, and environmental transformation. This was a new world not just for Europeans, but for Indians as well.

As colonial military expeditions aided missions to shatter and then remake Ohlone society, European animals also changed the land. In 1828 a French merchant visiting Santa Clara mission estimated that Santa Clara and San Jose missions grazed twelve thousand cattle and fifteen thousand sheep in the south bay hills. These herds had a profound and lasting effect on the landscape, from ridgetop to bayshore. Spanish livestock trampled or consumed bulbs, seeds, and fields of greens managed by native villagers, helping to destroy Indian economies and making them dependent on missions for food. Too many livestock also changed the land itself. The enormous herds sheared off California's perennial bunchgrasses and pulled them up by the roots. Slow-growing perennial grasses rather than grazing-resistant annuals, bunchgrasses were unable to recover. Winter rains washed the naked soil off in great sheets. Erosion was most concentrated in those areas where cattle were thickest and had been present longest, particularly on the mission lands of the south and east bay. On the extensive marshy plain near the mouths of Coyote Creek and Guadalupe River-not far from what is now downtown San Jose-swollen streams annually piled up fresh deposits of mud. Years later, a cowboy on the Alviso rancho described the continuing mudflows. Harry Wade explained that "high waters" had made "deposits of sand" so extensive that the bayshore road could no longer be traced and had to be abandoned. Storms dumped sheets of mud as much as eighteen inches thick that wiped out roads and filled in the bay.

Disaster planted the seeds that later yielded the fruits of survival. By joining the missions, San Francisco Bay's Indian peoples passed into a familiar category, one with legitimacy in the Spanish and later Mexican community. By 1848 Ohlones were sufficiently acculturated-dressing, speaking, and eating like the mestizos around them-that to American eyes, at least, they often merged into the "Mexican" category. This may have saved their lives. In general, Americans arriving during the gold rush did not practice mass murder on the former Mission Indians as they did the less-acculturated native peoples of northern and eastern California. The bayshore Indians survived by becoming Mexican. They mixed with the Spanish and mixed-descent Mexican population.

In practice, "becoming Mexican" meant fitting into the Mexican economy. Indians' labor gave them a place in the strange hybrid of American California and therefore a kind of future. In 1847, California's military governor, Richard Barnes Mason, and his secretary of state, Henry Wager Halleck, created a code regulating Indian behavior. The document paralleled the Black Codes that ruled the actions of blacks in the American South. Historian Albert Hurtado argues that the code, which restricted Indian movement, did not make Indians into slaves. But in other ways, the parallel with the Black Codes is striking. Indians' only protection came from their status as laborers. In February 1847 the naval commander John B. Montgomery proclaimed that Indians in the district of San Francisco should not be held as slaves. Every Indian would instead have a contract-but one that could be revoked only if the Indian could prove abuse. Indians without contracts were liable to forced labor in public works. The result of the code was that Bay Area Indians were again denied the chance to choose their own places of residence and economic activity. Indians who been forcibly removed from their lands by the missions, then cheated in the Mexican dispensation of the mission lands, now found themselves barred from any return to the bayshore. Yet some Indians did manage to return, and the story of one man and his land brings that relation into sharper focus.

When Mexican Californians closed California's Franciscan missions in the 1830s, they thought they would make Indians into Mexican citizens by granting them individual farms. This Enlightenment ideal of citizenship had particular resonance for Mexicans, who had long struggled to break down and incorporate Indian peoples throughout the Americas. Spanish administrators in New Spain and their Mexican successors alike obsessed about their failure to fundamentally change communal Indian villages. Whether granting land to California's Indians might have actually made them "citizens" of Mexican California is unknowable because so few Indians received any land. Of five missions around San Francisco Bay, with several thousand Indian inhabitants, historians have positively identified only one Indian who received a land grant.

Iñigo (or Yñigo) Lope was born around 1800 in an Ohlone village near the southwestern shore of San Francisco Bay. Together with the remnants of his family group, Lope abandoned his village and moved into nearby Mission Santa Clara, where he was baptized and given the Spanish name "Iñigo," the name he would use publicly for the rest of his life. As a mature man, Iñigo worked as a scout for the Spanish and Mexican military. He guided expeditions to recapture runaways from the missions and to pursue Indian stock thieves, who took refuge in the tule swamps and grasslands east of the bay. In the 1830s, Iñigo appealed for and was granted a parcel of land formerly part of Mission Santa Clara stretching inland from the bayshore near present-day Sunnyvale, California. Scholars Randall Milliken and Lawrence Shoup speculate that Iñigo's unique success in receiving mission land derived from a combination of powerful patrons and his service as a Mexican soldier. Perhaps it did not hurt that Iñigo asked for land that, from the Mexican perspective, was the least valuable property in the region. Iñigo's grant, which became known as Posolmi, was a rough square two miles on each side. Posolmi included a few hundred acres of seasonally flooded meadows, at least one artesian spring, and large expanses of marshlands bordering on San Francisco Bay. Shoup and Milliken deduce from archaeological and documentary evidence that Iñigo sought this particular land for good reason. Shellmounds on the property contained the bones of Iñigo's own ancestors. Iñigo's home village most likely sat on this very land before his family moved into the Santa Clara mission and the village rotted away.

The fate of Iñigo, his family, and their property is poignant. Disease swept away his wife and children. After his death Iñigo's powerful patrons divided his land and sold it. Farmers plowed over the site of his shellmound, exposing the graves of his ancestors and many of their possessions. Both bones and tools became souvenirs for the curious. A newspaper story in the 1920s mentioned that a skull from the shellmound had been put on public display. Destroying the shellmound scattered Iñigo's own history and the history of his people. Little record remained of their millennia-long occupation of this site. Similarly, the fate of the land since Iñigo's death has made its past invisible. Settlers cut the willow groves that once graced the property. In their thirst for irrigation water farmers drained the aquifer that fed Posolmi's springs. Without the springs, wetlands that had attracted clouds of waterfowl dried up.

The fate of Mexican Californians and their productive landscapes is almost as forgotten as that of Iñigo and his people. Spanish and Mexicans remade the Bay Area as a more fertile version of Castile with cheap Indian labor. Their economy centered on grazing and small-scale irrigated agriculture, where Indians had relied on a variety of seasonal resources. The Americans who replaced Mexicans as the owners of the bayshore would bring with them a very different idea of productivity: one that valued the intersection of land and water as a key element in an economy based on exchange.

Americans took California as the prize of a war fought largely on far distant battlefields. Around San Francisco Bay, the Mexican-American War was a brief affair. In early January 1847 Americans and Mexicans fought briefly in the area around Mission Santa Clara in the south bay. The "Battle of the Mustard Stalks" was the only sizeable engagement fought in northern California, and it ended Mexican rule in the northern part of the province. Ownership of the lands around San Francisco Bay was never again in doubt. American military commanders now assumed the role of an occupying army and provisional government. U.S. law applied only to American territories, while Mexican California was an occupied land. U.S. military governors thus found themselves enforcing Mexican laws, including those regulating the sale of public lands.

By 1847, Spanish and Mexican governments had long since granted most land located within striking distance of navigable waterways like the bays, ocean, and rivers. Americans who swarmed into California at the news of the war, and in far greater numbers following the discovery of gold in the foothills of the Sierra Nevada mountains, soon discovered that American governance did not mean access to free land. This was a surprise. After the Louisiana Purchase of 1806 and subsequent purchases of lands from Indian tribes and European nations, Congress had swiftly placed the new lands in the hands of the General Land Office for sale to settlers. Now, in 1847, Americans in California expected to purchase land. At the least, given that no surveys had yet been done, Americans hoped to be able to hold land for later purchase by "preemption," or homesteading. Instead, land-hungry Americans discovered a mess. California did not become a state until 1850. In the meantime, its land surface was the property of the federal government, which acted slowly in organizing a territorial government. Absent state or federal land surveyors, land could not be legally mapped, divided, or sold. More importantly, the 1848 peace treaty signed by Mexico and the United States-a treaty whose negotiations had dragged on for more than a year after fighting had ceased in Mexico, and nearly two years after the end of hostilities in northern California-guaranteed that Mexican law would be respected regarding landownership. American negotiators promised that Mexican landowners would keep their land.

California was the most remote province in both the Spanish New World empire and later the Mexican Republic. Its remoteness gave it some distinctiveness, but the basic pattern of landownership and use was similar to other regions of northern Mexico. Control of labor, not landownership, was the overriding concern. Franciscan missionaries, supported by Spanish soldiers, coerced Indian peoples into providing that labor. Mission Indians worked fields and herds in a pastoral and agricultural economy intended largely for local consumption. After the Mexican government passed the Secularization Act of 1833, mission lands in California were supposed to be granted to individual Indians, but instead a handful of men, often cronies of the Mexican governors, received immense estates. These private properties seemed like a significant departure from the communal practices of the missions. Yet these landed estates relied on the same pastoral economy and Indian labor that had supported the Spanish missions.

On the eve of the American conquest, therefore, most land surrounding San Francisco Bay was held in enormous ranchos, owned by immigrants from Mexico or their descendants and worked by Indians. The ranchos claimed land from the edge of the bay upward. The most valuable lands for a grazing economy were not those lying along the bay, with their access to salt marsh and bay resources, but rather the grasslands of the surrounding uplands. Ranchos were mapped by simple, almost abstract representations called diseños that gave only vague descriptions and usually based boundaries on prominent natural features ("the edge of the bay"; "the top of the valley") or by referring to a neighboring property. Mexican-era land grants closely matched the former mission boundaries they derived from, and the divisions between grants were designated by creeks, the edge of the bay, or occasionally straight lines corresponding not to a survey but rather from point to point. Mexican law required the grantee to live on the land and prohibited land transfer through donation, sale, or use of land as collateral for a loan. This republican notion of land was intended to attract and keep settlers in California, not to make them wealthy through speculation. But these restrictions and the vagueness of Mexican-era property boundaries were not problematic in a society whose notion of property was based on using rather than selling land. Ownership for Mexican Californians rested more on occupation and use of land than on deeds or legal description.

The 1848 treaty meant that Mexican rancheros could keep their land, since their title was legal. But there was a complication. Mexican-era land grants were vaguely defined, with boundaries marked by trees, mountains, or bodies of water. This imprecision presented legitimate Mexican land grantees with the opportunity to fraudulently expand their holdings. Even more serious, entirely false grants might be fabricated. In reaction, Congress created a land commission to determine legal ownership of the Spanish and Mexican land grants. But the commission created as many problems as it solved. It proved very difficult for grantees to prove their title. U.S. land commissioners forced Mexican landholders into court to prove the legality of their titles. Legal fees piled up. In the long run, most grantees won their cases, only to lose their land to the lawyers who represented them. More immediately, the litigation over land titles threatened to halt sales of any land in California. This encouraged squatting. It also led to the enormous expansion of the only clearly American-owned land in California, the bayfront of tiny Yerba Buena.