Route 123 is a four-lane boulevard with a median strip for its entire length. Its southern terminus is at the underpass of Interstate 580 in Oakland. Going north, it passes through the cities of Emeryville, Berkeley, Albany, and El Cerrito. It briefly turns on Cutting Boulevard before entering Richmond at its northern terminus under Interstate 80. San Pablo Avenue is sometimes used as an alternate route to the Eastshore Freeway when that freeway becomes very congested. Major intersections along this route include 40th Street, Ashby Avenue, University Avenue, Gilman Street, Marin Avenue, Central Avenue and Cutting Boulevard. Continuing on San Pablo Avenue past Route 123's southern terminus eventually leads to downtown Oakland and Oakland City Hall where San Pablo Avenue ends. Continuing on San Pablo Avenue before Route 123's northern terminus leads to the cities of San Pablo, Pinole, Hercules, Rodeo, and Crockett. In Hercules, San Pablo Avenue meets the terminus of State Route 4 near Interstate 80, and, after a discontinuity bridged by Parker Avenue in Rodeo, the road approaches the Carquinez Bridge and arrives in Crockett as Pomona Street. An AC Transit Rapid Bus runs along San Pablo Ave. from Downtown Oakland to Contra Costa College in San Pablo. The express bus line was put in place after a Metropolitan Transportation Commission study determined that it would be more cost-effective than a previous proposal to install light rail along the route. The BART system runs its Richmond leg parallel to the route up to the El Cerrito Del Norte station. The Alvarado Adobe is located by the San Pablo City Hall on the corner of San Pablo Avenue and Church Lane. SR 123 is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.
History
San Pablo Avenue is one of the oldest existing roads in the East Bay. It originated in the Spanish colonial era as the Camino de la Contra Costa and was legally a "camino real" until Mexico won its independence in 1821. It ran from the Encinal landings of the Rancho San Antonio northward along the bayshore, then eastward just inland of the Carquinez Strait. It was the principal thoroughfare for the scattered ranches throughout this part of the East Bay. The name persisted into the American era when it was still called the "Contra Costa Road". On July 15, 1852, the Court of Sessions of Contra Costa County ordered the construction of a more direct and somewhat improved road along the same general route between the Rancho San Pablo and Oakland, which consequently became known as "The San Pablo Road". This segment subsequently became today's "San Pablo Avenue". In 1927, this road was designated as part of the Lincoln Highway, the nation's first transcontinental road upon the opening of the new highway bridge across the Carquinez Strait. Prior to the construction of the Eastshore Highway, San Pablo Avenue was the main north-south route through the northern East Bay, carrying the designation U.S. Route 40 north of University Avenue in Berkeley. U.S. 40 was moved to the new highway after it was built, and about 25 years later took its current designation of Interstate 80. San Pablo Avenue was Business U.S. 40 until 1964. During 2005–06, San Pablo Avenue was repaved and otherwise rehabilitated by Caltrans. Portions of San Pablo Avenue, particularly in Berkeley, Albany, and El Cerrito, are slowly transforming, with a mix of trendy shops, restaurants and condominium developments. In the early part of the 20th century, a streetcar line ran on San Pablo between Richmond and Oakland. Part of the Oakland segment of these tracks up to Grayson Street in Berkeley were used during World War II for the Shipyard Railway of the Key System which transported workers from the Key System's hub in Emeryville to the Kaiser Shipyards in Richmond.
