United States Geography

California is home to more than 10 percent of all Americans and a central element in the American cultural fabric. Although more than two-thirds of native-born Americans live in their state of birth, fewer than half of all Californians were born in the state. Rather, California has been an important destination for U.S. internal migration in nearly every decade since 1850.

By most of the criteria used in the definition of regions, California is not a single unit. The agricultural population of the Imperial Valley in the southeast is quite different from the urban population of San Francisco. The striking flatness of the San Joaquin Valley is in sharp contrast to the ruggedness of the Sierra Nevada mountain range. There are broad areas of desert in the southern interior and heavily forested slopes along the coastal north. The lowest and highest elevations in the conterminous United States, Death Valley and Mount Whitney, respectively, are almost within sight of each other.

California's dramatic and varied physical environment has played a strong role in the state's settlement. Most of the state's population today is crowded into a small part of its territory, constricted by expanses of rugged topography and a widespread lack of water. In fact, this mecca for America's worship of the outdoor life surpasses every other state in its level of urbanization. Several factors account for this, but the restrictive aspects of the physical environment are certainly important.


The coast of California is lined by long mountain ranges that trend in a generally northwesterly direction. They are collectively called the Coast Ranges. Most are not particularly high--summits are between 1,000 and 1,600 meters. They are heavily folded and faulted as a result of the pressures of plate contact just to the west. The California earthquake fault zones follow the same northwesterly trend as the Coast Ranges.

Small earthquakes are common across large sections of the region, especially from the San Francisco Bay area southward to near Bakersfield and from the Los Angeles area southeastward through the Imperial Valley.

To the east of the Coast Ranges for much of their distance lies the Central Valley. This valley is extremely flat, extends 650 kilometers from north to south, and is nearly 150 kilometers wide in places. The Central Valley was originally a massive extension of the Pacific Ocean, open to the sea only at San Francisco Bay. A recipient of the erosion material carried off the western slope of the Sierra Nevada, this former section of the sea has been filled in with sediment. The result is a low-relief landscape rich in potential for large-scale agricultural pursuits.

To the east of the Central Valley, the Sierra Nevada rise gradually and have been heavily eroded. In contrast, the eastern face of the mountains offers a dramatic change in elevation. These are fault-block mountains, large rock masses that rose as a whole unit, and the eastern side was lifted far more sharply than the western face. Because they reach high elevations and contain few passes, the Sierra Nevada have proven a major barrier to movement between middle and northern California and areas to the east.

Two other landscape areas, less identifiably Californian, complete the state's topography. In the north, the mountain-valley-mountain pattern breaks down, and much of the northern tier is generally mountainous. The central plateau portion, directly north of the Central Valley, contains two of the state's major volcanic peaks, Mount Lassen and Mount Shasta. To the southeast of the Central Valley, the Great Basin of the interior is composed of low-lying mountains interspersed with large areas of fairly flat land.

Variations in California's climate and vegetation are nearly as great as the diversity of its topography. Of greatest importance for precipitation is the frequent movement of moisture-laden air southeastward out of the northeast Pacific. The distance southward that storm systems from this air mass can move is influenced substantially by a stable high-pressure center usually found off the west coast of Mexico. Such a stationary center blocks the southward movement of storms emerging from the maritime air mass and forces the moisture-producing system eastward onto shore. This blocking high tends to drift northward during summer and southward during winter.

A definite north-south gradient in average annual precipitation occurs in California as a result of these air masses; the north is much more moist on the average than the south. Furthermore, summers are characteristically drier than winters, especially in the south. In summer, southern California frequently experiences long periods during which there is no rainfall. Consequently, the wooded mountain slopes grow dry as tinder. Forest fires, another of the region's recurring environmental problems, are most frequent in late summer and fall, toward the end of the long dry period.

The coast north of San Francisco has temperatures with relatively little seasonal variation, plentiful year-round precipitation, and frequent periods of overcast skies.

The Central Valley is much drier than the coastal margins of the state. Annual precipitation is usually less than half that found at a similar latitude on the western slopes of the Coast Ranges. For example, Mendocino, on the coast north of San Francisco, averages 92 centimeters of precipitation annually, while Yuba City, directly east of Mendocino in the heart of the Sacramento Valley, averages only 52 centimeters. Southward, coastal San Luis Obispo averages 52 centimeters, while inland Bakersfield must make do with only 15 centimeters annually.

Summer temperature differences between coastal and inland points at a similar latitude are equally dramatic. San Luis Obispo's average July temperature is 18C; the average for Bakersfield is nearly 12C higher. Daytime high temperatures in San Francisco in late summer are usually under 27C, while Stockton, 100 kilometers east, is baking in temperatures over 38C. Much of this difference is the result of the moderating effect of the cold ocean current offshore and the usual pattern of afternoon and evening fog in summer along the coast.

To the interior of the Coast Ranges and the Sierra Nevada, in California's southeast, is a broad region of dry steppe or desert environment. During the late summer months, dry winds occasionally press westward to the coast, bringing extremely low humidity and temperatures that may register more than 40C. The southeastern interior area of California receives, on the average, less than 20 centimeters of precipitation annually.

Vegetation patterns closely parallel variations in climate in the state. Nearly all of lowland southern California and the area east of the Sierra Nevada-Cascade ranges is covered with sage, creosote bush, chaparral, and other characteristic desert and semidesert growth. The Central Valley and the valleys of the southern Coast Range are somewhat better watered than areas farther south; they are steppe grasslands. Wrapping around the Central Valley and following the coast from Santa Barbara to Monterey Bay are mixed open forests of live oaks and pines. The coast from Monterey Bay northward is the home of the redwoods, the world's largest trees. At higher elevations in the Coast Ranges and Sierra Nevada are mixed forests of pine and fir, and high in the Sierra Nevada are subalpine hemlock-fir forests, including those of the sequoia.


Perhaps California's greatest disadvantage, at least until recently, is its location at the far western periphery of the United States, some 3,500 kilometers from the most important areas of economic demand and supply in the country. This relative isolation is compounded by the nature of most of the land that lies between the Sierra Nevada and the South and the Midwest, a broad section of the country that generates little local freight.

More than anything else, climate has been the key in overcoming the state's apparent locational disadvantage; climate has been important to both the state's settlement history and its agricultural development.

The pre-European American Indians in California were hunters and gatherers. For food they depended on either seafood or grains and nuts that could be collected in the wild and ground into flour. There were few large tribes. Instead, most groups were organized into small units of perhaps 10 to 20 families. At the time of the first European arrival in the Americas, perhaps 1 Native American in 10 lived in what would become California.

Although Spanish explorers brushed the edge of California in the mid-1500s and claimed it as part of Spain's large North American holdings, they basically ignored it for the next two centuries. Not until concern arose over British and Russian expansion in western North America in the late 18th century did Spanish missionaries establish a string of missions from San Diego to Sonoma, near San Francisco. These mission settlements were joined by presidios (forts) and a few pueblos (towns). During the next few decades, the Spanish and Mexican governments granted a series of large landholdings (ranchos) to immigrants. Still, the area remained peripheral; the towns were small and ramshackle, and hides and tallow were the ranchos' most important exports.

Following U.S. seizure of California in 1846, a great gold strike in the foothills of the central Sierra Nevada in 1848 brought the first significant change in the region's settlement fortunes. Within a year, 40,000 people had come to the gold fields by sea, passing through San Francisco harbor. Perhaps as many more came overland. By 1850, California was a state. The frantic period of the gold rush lasted only a few years, but it succeeded in breaking the state's isolation from the rest of the country.

Southern California, the center of Spanish occupation in the state, did not share in the early population expansion, but the completion of railroads going west in the 1880s brought a sudden end to the area's quiet existence. In an effort to create a demand for their facilities, the railroads advertised widely for settlers, aided new arrivals in finding housing and jobs, and lowered fares. During the first southern California land boom, between 1881 and 1887, the population of Los Angeles grew from 10,000 to 70,000.

A large number of crops were also introduced into southern California during this period and in the years following, including the navel orange, the lemon, the Valencia orange, the avocado, and the date. They were in demand in eastern markets, and, at that time in the United States, only southern California could provide them in large quantities. Agriculture was to remain the backbone of southern California's economy until early in the 20th century.


California, by some measures America's most urbanized state, is at the same time its most agricultural state in terms of total farm income. In 1988, the market value of agricultural products sold in California was $16.6 billion. California's agriculture, although typified by its many specialty products, is, in fact, broadly based, thanks to the variety of climatic regions and the market demand of its own large population.

Many of the specialty crops are sensitive to variations in climate or soil type. The Coastal Range valleys that open onto the Pacific are frequently foggy and have moderate temperatures. Vegetables such as artichokes, lettuce, broccoli, and brussels sprouts grow well under such conditions. The varietal grapes that people often feel produce the best of American wines need a mild, sunny climate such as that found in the inland Coastal Range valleys around San Francisco. The grapes of the San Joaquin Valley and of southern California, where summer temperatures are much higher, are used for table grapes, raisins, and for what some wine drinkers consider less distinguished wines. Most flowers grown for seed in the United States are planted in the Lompoc Valley west of Santa Barbara. Navel oranges and lemons are grown almost exclusively along the coast and the interior surrounding the Los Angeles Basin.

The importance of many specialty crops in California does much to explain why the state's farmers have had such success in penetrating the markets of the distant East. These crops can be grown, or at least grown on a large scale, in only a few parts of the country. Most require long growing seasons. Thus, there is no local competition in the demand areas. Southern California, especially the Imperial Valley, is also able to provide vegetable crops during the winter season, when competition is minimal and sale prices are at a maximum.

Although California produces many agricultural products, local areas tend to specialize in the growth of one or a few crops, and some of California's specialty crops are grown by only a handful of farmers. In the San Joaquin Valley, some landholdings extend over many thousands of hectares.

California's agriculture has created a massive demand for water across much of the state. Nearly all of the state's cotton, sugar beets, vegetables, rice, fruits, flowers, and nuts are grown on irrigated farmland. California has more farmland irrigated than any other U.S. state, about 3.5 million hectares, and the state's farmers use more than one-fourth of all the irrigation water used in the country. On the average, irrigated land in the state receives about 1 meter of "artificial" water annually.

Crop selection at a location depends on water availability as well as soils, drainage, terrain, and growing season. But the potential for irrigation is usually critical. A transect across the San Joaquin Valley finds livestock grazing in the Sierra foothills; dry farming for grains in the flatter, but still too high for irrigation, land below; irrigated fruit trees and vine crops in the better drained soils near the valley floor; and irrigated field crops such as cotton and vegetables on the flat valley floor.

Some 70 percent of the state's precipitation falls in the northern mountains and valleys and in the Sierra Nevada, where few farms or urban places exist, whereas 80 percent of the water for irrigation is used in the drier south. Of the state's major farming regions, only areas north of San Francisco and a few coastal valleys to the south receive as much as 50 centimeters of precipitation in an average year.

Farms are the principal users of water, but it was the cities that initiated the development of the state's tremendous water movement complex. At the beginning of the 20th century, Los Angeles outgrew its local groundwater supplies and looked for a supplementary source in the Owens Valley, east of the Sierra Nevada and some 300 kilometers north of the city. By 1913, the Los Angeles Aqueduct was carrying water to Los Angeles. This aqueduct still provides half the city's needs. In 1928, Los Angeles and 10 other southern California cities formed the Metropolitan Water District to develop an adequate water supply for their area. Today, the Metropolitan Water District serves six counties, over 130 cities, and half of California's population.

Perhaps the most spectacular episode in the state's water history occurred in 1905 in the Imperial Valley. In 1901, private groups constructed canals to carry water from the Colorado River into the Imperial Valley; the result was an immediate agricultural land boom. Then, in February 1905, the Colorado River flooded, broke out of its channels, and flowed into the irrigation ditches. Before a massive effort returned the river to its channel in the fall of 1906, 1,100 square kilometers of the valley had been filled by the Salton Sea, a body that still exists, its size maintained by the ongoing drainage from irrigated farmland in the valley.

In the 1940s, the federal Bureau of Reclamation began the Central Valley project to improve the local availability of irrigation waters in the Central Valley. Today, water removed from the Sacramento River by the Delta-Mendota Canal flows southward along the west side of the San Joaquin Valley to Mendota, where it is put into the San Joaquin River. Thus, most of the normal flow of the San Joaquin River can be used for irrigation in the southern part of the valley, the state's leading agricultural region.


Despite California's agricultural importance nationally, its population is overwhelmingly urban and still increasing. Most of the state's population lives in one of its two major urban regions, one centered on Los Angeles, the other on San Francisco.

The land boom of the 1880s led to the establishment of several score of cities scattered across the Los Angeles Basin and the southern California coastlands. As their populations increased, these communities squeezed out the intervening rural lands that formerly separated them spatially.

Most of the 300-kilometer stretch of coastline from Santa Barbara to San Diego is now occupied by one long megalopolis, the home of about 15 million Californians. The entire complex is basically a creation of the 20th century. Thus, many of the elements of eastern cities placed on the landscape during the 19th century and the early 20th century are not present in Los Angeles. Among these missing features: four- or five-story walk-up apartment buildings, warehouses of about the same elevation, fixed-rail elevated or underground public transportation lines.

The most important stimulus in the southern metropolis has been the family automobile. Fully half of the central portion of Los Angeles has been surrendered to the automobile, either for roadways or parking. The urban area's dense system of freeways makes possible fairly high-speed movement across much of the metropolitan region. The Los Angeles area has more cars per capita than any other part of the United States and only a minimal public transportation system.

Finally, Los Angeles is a city without a center. The traditional single central business district as a focus of urban activity barely exists here. Los Angeles is really many cities that have grown together as they increased in size; 14 of these cities currently have populations of more than 100,000. The absence of a dominant central business district results in part from the continued existence of independent centers for each of these communities.

Although the area is not without resources, their overall importance is not overwhelming. In addition to agriculture, petroleum production is important; three of the country's major fields are in southern California. Offshore development began in 1965. The heavy demand for petroleum products, especially gasoline, results in the local consumption of virtually all of southern California's production.

Southern California is known worldwide as the location of Hollywood, long the center of America's motion picture industry. In the early days of filmmaking, outdoor settings and natural light were the norm. The area's cloudless skies and short cold-temperature periods made its streets and fields a fine home for countless motion pictures. Los Angeles remains one of the centers of American filmmaking and television, but today the motion picture industry plays only a small role in the metropolitan area's economy, employing less than 2 percent of its workers.

Its climate and its varied scenery, especially along the coast, early made southern California one of the country's centers of outdoor recreation. Today, these natural advantages have been supplemented by some of the country's largest and best-developed recreation facilities. Balboa Park in San Diego, with its excellent zoo, Knott's Berry Farm, and Marineland are major attractions. Disneyland has become an American phenomenon and the main destination of countless tourists.

Southern California is also the major destination for Latin American and Asian migrants entering the United States. More than one schoolchild in four in the Los Angeles school district speaks one of 104 different languages better than English.

Recent migrants especially often settle in ethnic neighborhoods. Little Tokyo, long a part of the city, has a renewed vibrancy. Monterey Park in the San Gabriel Valley is 50 percent Asian, making it the most heavily Asian city in the mainland United States. A rich diversity of ethnic restaurants, many found within ethnic enclaves, dot the city.

Still, all of this does not add up to resource support for 15 million people. Heavy resources, such as coal or iron ore, are virtually nonexistent. San Diego has a good harbor, but Los Angeles's harbor, entirely human-made, is only average.

However, southern California has profited from government spending far more than most other areas of the country. California receives about 20 percent of all Department of Defense spending and nearly half of that of the National Aeronautics and Space Administration. San Diego is the West Coast home of the U.S. Navy, and the navy is easily the city's principal employer. San Diego has relatively little manufacturing employment for an urbanized area of over 2 million, surely an important part of its claim to be one of America's most livable cities. Also, electronics--where the value added by manufacture is high and worker skills particularly important--has been a major contributor to the southern California economy.

Los Angeles has a higher dollar volume of retail sales than the New York metropolitan area, and the value of its manufactured goods is also higher. A decade ago, the city passed San Francisco as the West Coast's financial center; it ranks second nationally to New York City in banking deposits. The twin ports of Los Angeles and Long Beach together form the fastest growing major cargo center in the world. The dollar value of their import-export ocean-borne cargo now easily surpasses that of the Port of New York and New Jersey.

By comparison with their upstart competitors in the south, San Franciscans choose to view their city as old and cosmopolitan. The city was the northern core of Spanish and Mexican interest in California. It served as the supply center for the California gold rush. By 1850, it was the largest city on the Pacific Coast, a ranking it maintained until 1920. The completion of the first transcontinental railroad in 1869, coupled with the city's size and its excellent harbor, made it not only the focus of western U.S. growth but also the key location for U.S. commerce with the Pacific. Into the city came large numbers of immigrants from Asia, especially Chinese, plus substantial numbers of other foreigners. They created a cosmopolitan ethnic mixture that remains a readily apparent aspect of the city's character.

The romantic flair of its early history is one piece of the mosaic that makes San Francisco among the most popular of American cities. Its physical geography provides a splendid setting for a city: steep slopes that offer dramatic views of the Pacific Ocean or of San Francisco Bay, coupled with a mild climate that escapes the occasional staggering summer heat of southern California.

The city of San Francisco is currently home to fewer than one-eighth of the San Francisco Bay region's 5.4 million people. Hemmed into its small peninsula, the city is actually losing population while the entire urban area grows.

The Bay Area today is really composed of several different areas, each with its own character. The East Bay is the most varied, with a mix of college students, large tracts occupied by middle-class residents, and most of the port facilities and heavy industry of the region. The San Jose-South Bay area is upper middle class, with new houses, fine yards, and major regional shopping centers. Along the Bay north of San Jose is Silicon Valley, so named because of its concentration of businesses engaged in chemical and electronics research associated with production of computer components. North of the Golden Gate Bridge, the cities are smaller, there is little manufacturing, and the conflict between agricultural and urban land use is sometimes obvious. Here are found the well-to-do urbanites searching for a place in the country. The city of San Francisco itself, with its grid pattern of streets incongruously placed on a hilly terrain, its closely spaced late 19th- and early 20-century housing, and its ethnic diversity, maintains a special appeal.

Unlike Los Angeles, the existence of a major urban center in the Bay Area is not surprising. Its excellent harbor and good climate are important site factors. By volume, it is the major Pacific port in North America. Its rail and highway ties to the East at least equal those for any other West Coast city. Just as Megalopolis is America's hinge with Europe, San Francisco is its hinge with Asia.

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Source: U.S. Department of State