San Francisco Bay Area, California

San Francisco and the Golden Gate Bridge.

The San Francisco Bay Area is an urban region in the US state of California. Traditionally, the center has been the city of San Francisco, which has a population of 815,000. The largest city, however, is San Jose, which has a population of 983,000 and is the center of Silicon Valley. The agglomeration extends over 7 to 9 counties, depending on the definition and has a total of 6,961,000 to 9,546,000 inhabitants (2021).



According to mcat-test-centers, the San Francisco Bay Area is located in western California, on the Pacific Ocean. It is usually considered part of Northern California, although that term mainly refers to rural California and the Bay Area is a region of its own. San Francisco is located about 130 kilometers southwest of the capital Sacramento and 560 kilometers northwest of Los Angeles.


San Francisco is known for its attractive landscape and climate. The region has large bays, actually consisting of San Francisco Bay in the south and San Pablo Bay in the north. The core of the urban area is along the San Francisco Bay, and relatively little along the Pacific Ocean to the west. The region has several mountain ridges that are largely undeveloped. The mountains are mostly between 600 and 1,300 meters high. The southern part of the San Francisco Bay is also known as Silicon Valley, a broad valley in which the city of San Jose is located. The shores of Silicon Valley are formed by swamps and wetlands. Immediately east of San Francisco Bay is a ridge, with a hotter interior beyond. The temperature differences between the San Francisco Bay and the interior are often striking.

To the north is San Pablo Bay, which is bounded to the west and east by mountain ridges, but to the north by wetlands. Through a narrow strait it turns east into Suisun Bay, a shallow bay with wetlands to the north and east. To the east it merges back into the San Joaquin River delta, a green and low-lying area. To the east of this is the town of Stockton.

The climate of San Francisco is more temperate than in Southern California or the San Joaquin Valley. Particularly directly around the Pacific Ocean and San Francisco Bay, temperatures are often not very high, with average summer highs of 22-23°C. The region receives a moderate amount of precipitation. Sea fog is common around the Golden Gate. The city of San Jose is somewhat warmer than San Francisco, with average summer highs of 27-28°C. The inland suburbs are much warmer, with average maximum temperatures of 30-32°C in summer and significantly less precipitation.


San Francisco has traditionally been the center of the American technology sector, with IT and Internet companies in particular having a strong presence. Many corporate headquarters are in San Francisco while many Silicon Valley campuses and assembly centers are around San Jose. In addition, Oakland has an important port. The eastern part of the San Francisco Bay is much more industrial in character than the western side. Much energy-intensive activity has shifted to cheaper states because of high electricity prices. For example, the servers of many internet giants are not located in the San Francisco region, but in cheaper states such as Washington.

San Francisco is generally considered one of the most expensive metropolitan areas in the United States, the cost of living is significantly above the national average, especially housing is extremely expensive. This has resulted in the formation of a large number of suburbs in the less attractive interior, in Alameda and Contra Costa County. In 2015, the median home prices in San Francisco were $1 million and these are often relatively small homes. In 2015, the median rent increased to $2,700 – 5,200 per month. [2]

Urban construction

The Bay Area conurbation is the most fragmented in the United States. This is due to the various bays, peninsulas and mountain ridges. The population is concentrated along a number of corridors. The city of San Francisco is located on the northern tip of a large peninsula. To the west of this is the Pacific Ocean, to the east of it San Francisco Bay. On the east side of the bay is the suburban city of Oakland, on the south side is its largest city, San Jose. To the north is San Pablo Bay, with mostly small suburbs surrounding it. In the northeast it turns into Suisun Bay, along which a number of distant suburbs lie. East of San Francisco Bay is a ridge, with a series of suburbs beyond. Due to the many natural obstacles and extreme house prices, the urban area has not been able to grow as much in recent years. Between 2000 and 2010, the growth was barely half the average in the United States, a contraction set in at the end of the 2010s. In 2020-2021 there was a large population decline, in percentage terms the MSAs of San Francisco and San Jose shrank the most of the large agglomerations. The city of San Francisco in particular lost many inhabitants in a short time, but San Jose also fell below the limit of 1 million inhabitants in that period.

Population growth

Population growth by county. The overview below only includes the core counties of the urban area. Napa County (population 136,000) and Sonoma County (population 486,000) are often included in the metropolitan area, although Sonoma County with Santa Rosa as its urban center is still separate from the rest of the metropolitan area, mainly due to slow growth in Marin County.

Year San Francisco San Mateo Santa Clara alameda Contra Costa marin Solano total grow
1940 635,000 112,000 175,000 513,000 100,000 53,000 49,000 1,637,000
1950 775,000 236,000 291,000 740,000 299,000 86,000 105,000 2,532,000 +895,000
1960 740,000 444,000 642,000 908,000 409,000 147,000 135,000 3,425,000 +893,000
1970 716,000 556,000 1,065,000 1,073,000 558,000 206,000 170,000 4,344,000 +919,000
1980 679,000 587,000 1,295,000 1,105,000 656,000 223,000 235,000 4.780.000 +436,000
1990 723,000 650,000 1,498,000 1,279,000 804,000 230,000 340,000 5,524,000 +744,000
2000 777,000 707,000 1,683,000 1,444,000 949,000 247,000 395,000 6.202.000 +678,000
2010 805,000 718,000 1,782,000 1,510,000 1,049,000 252,000 413,000 6,529,000 +327,000
2020 870,000 762,000 1,931,000 1,680,000 1,166,000 262,000 453,000 7,124,000 +595,000
2021 815,000 738,000 1,886,000 1,649,000 1,161,000 260,000 452,000 6,961,000 -163,000

Road network

The highway network with toll roads in green.

See also San Francisco Bay Area HOV system.

The network consists of a number of Interstates, which form the main route network of the highway network. The US 101 can also be included in this category. The State Routes are usually short supplementary routes, most of which do not have a major through function. Some highways are very short, such as I-238, I-380, I-980 and SR-242. Due to the mountainous landscape, the number of through highways is limited, which are very busy. There are also 8 toll bridges over the different bays, which are sometimes very busy, especially the San Francisco – Oakland Bay Bridge between the two cities. All of these bridges are toll bridges, with the 4 major bridges over San Francisco Bay a $6 toll westbound only. The city of San Francisco has relatively few highways in terms of population and commuterism, and the highways that do exist are busy and congested.

Because the conurbation is relatively eccentric from the national road network, there is only one main route (I-80) serving the conurbation. The rest of the highways are regional or state highways.

Interstate Highways

There are two parallel highways between San Francisco and San Jose, the Bayshore Freeway (US 101) and the Junipero Serra Freeway (I-280). The Nimitz Freeway (I-880) runs between Oakland and San Jose. Interstate 680 forms the eastern bypass of the metropolitan area, connecting San Jose toward Sacramento. There are three highways connecting the metropolitan area with other parts of California. US 101 is the coastal route from San Jose to Los Angeles and from San Francisco to the north of the state. Interstate 80 is the connection to Sacramento and further east through the Sierra Nevada. Interstate 580 forms a northern bypass of Sacramento and leads through Oakland to Interstate 5, the highway to Los Angeles. The other highways have a regional importance. Interstate 380 is a short east-west connection in South San Francisco and Interstate 980 is a short connection through downtown Oakland.

State Routes

Several State Routes handle a lot of commuter traffic. Interconnecting the northern suburbs, SR-4 is a long-haul commuter route from Antioch to San Francisco. The SR-13 is a relatively short highway through Oakland. SR-24 connects Oakland to the eastern suburbs, around Walnut Creek. SR-37 is the northernmost east-west connection of the conurbation between Novato and Vallejo. SR-84 forms the southernmost toll link across San Francisco Bay between Palo Alto and Fermont. SR-85 is San Jose’s southern and western bypass. SR-87 forms a north-south axis through San Jose and finally SR -92. forms a toll link between San Mateo and Hayward.

List of freeways

Road name length first opening last opening max AADT 2016
Eastshore Freeway 53 km 1935 1960 275,000
Robert T. Monagan Freeway 21 km 1970 1970 130,000
Interstate 238 3 km 1956 1956 151,000
Junipero Serra Freeway 92 km 1963 1973 256,000
Quentin L. Kopp Freeway 5 km 1971 1976 161,000
MacArthur Freeway 129 km 1956 1991 254,000
Donald D. Doyle Highway 114 km 1960 1974 270,000
Interstate 780 11 km 1958 1962 66,000
Nimitz Freeway 74 km 1949 1958 277,000
John B. Williams Freeway 3 km 1969 1973 134,000
Bayshore Freeway 137 km 1947 1968 270,000
Cabrillo Highway 8 km 1965 1968 96,000
California Delta Highway 55 km 1953 2018 183,000
Warren Freeway 8 km 1951 1966 80,000
Santa Cruz Highway 13 km 1994 1994 176,000
State Route 24 22 km 1964 1970 200,000
Sears Point Road 35 km 1992 1992 98,000
Dumbarton Bridge 13 km 1982 1982 71,000
Norman Y. Mineta Highway 38 km 1965 1994 154,000
Guadalupe Freeway 14 km 1988 2003 169,000
J. Arthur Younger Freeway 29 km 1963 1975 153,000
Southbay Freeway 18 km 1961 1997 139,000
State Route 242 6 km 1963 1978 130,000


The highway plan of 1955.

San Francisco was one of the first cities outside the East Coast of the United States to have highways built. In 1936, Interstate 80 opened between San Francisco and Oakland, including the imposing San Francisco – Oakland Bay Bridge. A year later, the Golden Gate Bridge, over which US 101 runs, opened. After that, highway construction was halted for about 20 years.

New highways began building again in the mid-1950s, and at a rapid pace, as funding through the federal government ‘s Interstate Highway program was quick and easy. Nearly all highways were built in the next 15 years, and by 1970 nearly all of the region’s Interstate Highways had been completed. The major bridges in the region were also built at that time. In the early 1970s, a few missing links were opened, but attention then shifted from the highways to public transport, a policy that has hardly changed in the 40 years since.

However, there were not nearly as many highways around the fast-growing city of San Jose as elsewhere. This became a major problem as the city grew by tens of thousands of inhabitants each year. After a construction lull that lasted from the early 1970s to the mid-1980s, a number of new highways around San Jose were opened in the late 1980s and early 1990s. These are SR-85 as a southern bypass, SR-87 as a north-south route through downtown, and SR-237 on the north side of the city. There have been no significant freeway openings since roughly 1994, except for a few relatively insignificant links, such as a stretch of SR-4 in Hercules and I-580 in Richmond in the late 1990s.

After the Loma Prieta earthquake in 1989, it became clear that many highways would collapse in a major earthquake. That is why, from the 1990s, a large program has been carried out to make the structures earthquake-resistant, this is called a seismic retrofit. Some bridges have also been replaced or doubled, most notably over the Carquinez Strait between Contra Costa and Solano County in the north of the metropolitan area. Road widening is carried out sporadically in urban areas. One of the most prominent plans that has not been executed is the construction of US 101 as a freeway by San Francisco. North-south traffic must use San Francisco’s street network. One highway has been demolished, the short Embarcadero Freeway near downtown San Francisco. The overpass highway was damaged after the 1989 earthquake and was subsequently demolished. However, this is only a short section of 2 kilometers, which has been replaced by a wide and busy city boulevard.

Between 2002 and 2013, the eastern span of the San Francisco – Oakland Bay Bridge was replaced with a new one. The capacity of 2×5 lanes remained the same, but the new span does have emergency lanes. Construction costs totaled $6.3 billion.


The Richmond – San Rafael Bridge (I-580).

Bridge Route Length Opening date
Carquinez Bridge II I-80 1,056 meters 21-05-1927
San Francisco – Oakland Bay Bridge I-80 7,180 meters 12-11-1936
Golden Gate Bridge US 101 2,700 meters 19-04-1937
Carquinez Bridge II I-80 1,056 meters 00-00-1958
Richmond – San Rafael Bridge I-580 8,850 meters 01-09-1956
Benicia – Martinez Bridge II I-680 2,700 meters 00-00-1962
San Mateo – Hayward Bridge SR-92 11,265 meters 00-00-1967
Dumbarton Bridge SR-84 2,622 meters 00-10-1982
Carquinez Bridge I replacement I-80 1,056 meters 11-11-2003
Benicia – Marinez Bridge II I-680 2,700 meters 25-08-2007


No new highways are planned in the conurbation. Old plans envisaged a larger highway network than now, with mainly a few missing links that were still planned. Major changes to the highway network are not foreseen, however, and widening the highways is also not a high priority, partly because of the prioritization of public transport and the high costs of making a large number of structures earthquake-proof. Other projects include the large-scale conversion of nearly 1,000 kilometers of HOV lane to HOT lane.


Due to the limited number of highways, traffic flows are considerably bundled, so that congestion can easily arise. Congestion was extreme in the late 1990s due to the dot com bubble, then eased somewhat, but has increased dramatically since a new tech boom since circa 2005. The San Francisco-San Jose region is also extremely prone to traffic congestion because house prices have risen enormously and are no longer affordable for middle incomes. As a result, large distances are often commuted from the interior to San Francisco and San Jose. Traffic jams in the San Francisco area are starting earlier and earlier, especially on the San Francisco-Oakland Bay Bridge. The US 101 between San Jose and San Francisco is also extremely sensitive to traffic. In addition, the region has several highly congested routes where traffic jams can occur at any time of day, such as on I-80 between San Francisco and Sacramento, on I-580 from Oakland inland and on I-680 as a bypass of the East Bay to San Jose. I-880 between Oakland and San Jose is also prone to congestion due to the large volume of freight traffic. Congestion on the Golden Gate Bridge has been reduced somewhat with the installation of a zipper barrier, which reduces accidents, and the fully electronic toll collection and an upgrade of the connecting Presidio Parkway in 2015.

San Francisco Bay Area, California