Interstate 280

Interstate 280 is a major north–south Interstate Highway in the San Francisco Bay Area of Northern California. It runs from San Jose north to San Francisco, roughly paralleling the San Francisco Bay shoreline and the San Andreas Fault. Known for its scenic beauty through the Santa Cruz Mountains, it is often called the "World's Most Beautiful Freeway." The route serves as a critical bypass for the congested US 101 corridor and connects key Silicon Valley communities to San Francisco.

Route description

Beginning at a complex interchange with I-680 and I-880 in San Jose, it heads northwest through the western foothills of Santa Clara County. It passes near the headquarters of major technology firms in Cupertino and Los Altos before entering the forested slopes of the Santa Cruz Mountains. The highway traverses the scenic Sawyer Camp Trail corridor and the Crystal Springs Reservoir, managed by the San Francisco Public Utilities Commission, within San Mateo County. North of SR 92, it joins the Junipero Serra Freeway and passes by San Francisco International Airport before merging with US 101 for the final approach into San Francisco. Its northern terminus is at King Street and 6th Street in the South of Market district, near the San Francisco Bay and the Oracle Park baseball stadium.

History

The route was conceived as part of the 1955 California Freeway and Expressway System plan to provide a bypass west of US 101. Construction began in the early 1960s, with the first segment opening in San Jose in 1964. A significant engineering challenge was the construction through the Cahill Ridge area near the Crystal Springs Reservoir, requiring careful environmental planning. The final segment through San Francisco was completed and opened to traffic in 1973. The highway's designation was initially proposed as I-480, but this was changed following the cancellation of the Embarcadero Freeway project. Notable figures like John A. B. Fry of the California Division of Highways were instrumental in its routing and design, which emphasized preserving natural scenery.

Major intersections

From south to north, key junctions include the southern terminus at the I-680/I-880 interchange in San Jose. It intersects US 101 and SR 87 in San Jose, and meets SR 85 in Cupertino. Further north, it has interchanges with SR 84 near Woodside and SR 92 in San Mateo. It converges with US 101 just south of San Francisco International Airport and runs concurrently with it through the San Francisco county line. The final major junction is with I-80 and the San Francisco–Oakland Bay Bridge approach in San Francisco, before reaching its northern terminus.

Auxiliary routes

The primary auxiliary route is Interstate 280 Business in San Jose, which follows the Almaden Expressway. This route was part of the original legislative route for SR 82 and provides direct access to the Almaden Valley and Downtown San Jose. While not a full auxiliary Interstate, the related SR 82 (El Camino Real) runs parallel to much of the route from San Jose to San Francisco, serving as a historic frontage road and major arterial. The planned I-380 spur to San Francisco International Airport was never constructed as a full Interstate.