I-280 beginning at its interchange with State Route 1 in Daly City was built and dedicated as the Junipero Serra Freeway. One of the dedication signs (in Daly City) still indicates that the Junipero Serra Freeway is known as the "World's Most Beautiful Freeway" due to its scenic route though the San Francisco Peninsula. The portion of Interstate 280 between U.S. 101 and Interstate 880 is also named the Sinclair Freeway.
Bolded cities are officially-designated control cities for signs
The segment of the Junipero Serra Freeway between Cupertino and Daly City, has been called the "World's Most Beautiful Freeway" since its dedication in the 1960s. Drivers along this portion of Interstate 280 are treated to scenic views of the Santa Cruz Mountains to the west and San Francisco Bay to the east, and are isolated by hills from the cities to the east. Through much of this segment, the freeway is actually running just inside the eastern rim of the canyon of the San Andreas Fault. A particularly attractive six mile (ten kilometer) stretch of the freeway from Hillsborough to Belmont provides a beautiful look at Crystal Springs Reservoir, formed by water piped hundreds of miles from Hetch Hetchy Valley in Yosemite National Park, filling the bottom of the fault canyon.
For nearly all of its length, Interstate 280 runs roughly parallel and several miles to the west of US 101 (the Bayshore Freeway). Both freeways are north-south routes connecting San Jose with San Francisco; however, unlike I-280, the route that US 101 takes between the two cities goes entirely through urbanized areas. The majority of the population of the San Francisco Peninsula lives somewhere between Interstate 280 and US 101.
I-280 never intersects with Interstate 80, its parent interstate. The northern terminus of I-280 is within about a mile of I-80's western terminus (at the approach to the San Francisco – Oakland Bay Bridge), but the two interstates do not actually intersect. Although San Francisco has had several opportunities to connect I-280 to I-80, it has chosen to use the money for other purposes. Connecting the two freeways is considered to be politically and financially infeasible at this time, due to the city's strong anti-freeway stance. Instead, 280's northernmost extension primarily functions as a spur into Downtown San Francisco, as suggested by signage on northbound US 101 at its San Francisco interchange with 280 (see history section below).
Most of Interstate 280, from San Jose to Daly City, is designated as the Junipero Serra Freeway in honor of Spanish missionary Junípero Serra, who founded many of California's missions in the 18th century. A 26-foot (8 meter) high faux-sandstone statue of Father Serra kneeling and pointing over the freeway is located at a highway rest area just north of the Highway 92 intersection between the Bunker Hill Drive and Black Mountain Road exits on northbound I-280 in Hillsborough, and can be clearly seen by drivers in both directions. The segment of Interstate 280 north of Route 1 in San Francisco was originally named the Southern Freeway, but has since been officially renamed the John F. Foran Freeway. However, most San Franciscans still refer to it as the Southern Freeway. The section of I-280 between the James Lick Freeway and its end at Third Street and King Street is called the Southern Embarcadero Freeway.
The Junipero Serra Freeway is Route 280 from Route 1 in San Francisco to Route 17, as named by Assembly Concurrent Resolution 140, Chapter 208 in 1967.
Interstate 280 was added to the Interstate Highway System on September 15, 1955 as a route from San Jose north to San Francisco. This ran along the present alignment of I-280 south of San Francisco, but in San Francisco it ran north parallel to State Route 1, past the planned west end of Interstate 80, to the south approach to the Golden Gate Bridge. At that point, Interstate 480 began and headed east on Doyle Drive (U.S. Route 101), the Golden Gate Freeway, and onto the Embarcadero Freeway to reach the San Francisco – Oakland Bay Bridge. I-480 would continue south on the never-built Southern Embarcadero Freeway to meet the Southern Freeway (now I-280), and meet up with I-280 again near the Alemany Maze, which served as the 101A Bypass until I-280 was built. The I-280 number was approved on November 10, 1958.
In the 1964 renumbering, the Route 280 designation was officially applied to the planned route. This replaced SR 1 in San Francisco; the new SR 1 alignment turned northeast where I-280 now runs, quickly ending at State Route 82 (San Jose Avenue/Alemany Boulevard). SR 1 however continued to be signed along its former (and current) alignment, which had not been upgraded to freeway standards.
A realignment approved January 1968 took I-280 onto its current route. This ran along what had been SR 1, SR 82, State Route 87 and I-480 (downgraded to a State Route then), ending at Interstate 80 at the west end of the Bay Bridge. This change was made on the state level in 1968, restoring SR 1 to its current alignment and truncating SR 82, SR 87 and SR 480.
The section of I-280 between SR 92 (San Mateo) and SR 84 (Woodside) was not completed until the 1970s. Until then, traffic was routed on Cañada road between the two ends.
The short piece of I-280 between 3rd Street and SR 480 in downtown San Francisco was never built, and the piece from 3rd Street south to U.S. Route 101 was reconstructed after it was damaged by the 1989 Loma Prieta earthquake. The piece between SR 480 and I-80 was torn down along with the rest of the Embarcadero Freeway; all that remains of the I-80 interchange is a few ramp stubs, which will be removed as part of the San Francisco – Oakland Bay Bridge Western Approach reconstruction project.
|San Jose||R0.00||Continuation beyond US 101|
|R0.00||Southbound exit and northbound entrance|
|R0.37||1A||McLaughlin Avenue||Southbound exit and northbound entrance|
|R1.29||1B||11th Street, 10th Street||Signed as exit 1 northbound|
|R1.99||2A||Signed as exit 2 northbound|
|2B||Almaden Boulevard, Vine Street||Southbound exit and northbound entrance|
|R3.76||4||Race Street, Southwest Expressway||Northbound exit and southbound entrance|
|R3.99||4||Meridian Avenue||Southbound exit and northbound entrance|
|L4.66||5A||Leigh Avenue, Bascom Avenue|
|L5.41||5B||Signed as exits 5B (south) and 5C (north) northbound|
|4.57||6||Winchester Boulevard – Campbell||Southbound exit and northbound entrance|
|5.95||7||Saratoga Avenue – Saratoga|
|9||CR G2/Lawrence Expressway, Stevens Creek Boulevard|
|9.43||11||De Anza Boulevard|
|10.74||12||Signed as exits 12A (north) and 12B (south)|
|Los Altos||11.45||13||Foothill Expressway, Grant Road|
|Los Altos Hills||15.05||16||El Monte Road, Moody Road|
|18.38||20||Page Mill Road, Arastradero Road – Palo Alto|
|20.61||22||Alpine Road – Portola Valley|
|R1.61||24||Sand Hill Road – Menlo Park|
|R4.65||27||Farm Hill Boulevard|
|R6.60||Canada Road||No exit ramps|
|10.87||33||Southbound exit to SR 92 west is via exit 34|
|R12.32||34||South end of SR 35 overlap|
|Hillsborough||R14.22||36||Black Mountain Road, Hayne Road|
|R17.16||39||Trousdale Drive – Burlingame|
|Millbrae||R17.92||40||Millbrae Avenue||Northbound exit and southbound entrance|
|R18.52||41||Larkspur Drive, Millbrae Avenue||Southbound exit and northbound entrance|
|San Bruno||R19.28||41||North end of SR 35 overlap; northbound exit and southbound entrance|
|R20.22||42||Crystal Springs Road||Southbound exit and northbound entrance; former SR 117|
|R20.75||43A||San Bruno Avenue||Signed as exit 43B southbound|
|R21.02||43B||Signed as exit 43A southbound|
|R21.31||43A||Sneath Lane||Signed as exit 43B southbound|
|South San Francisco||R22.04||44||Avalon Drive||Northbound exit and southbound entrance; former SR 117|
|R22.62||45||Westborough Boulevard||Northbound exit is via exit 44|
|Daly City||R24.20||46||Hickey Boulevard – Colma, South San Francisco|
|R24.63||47A||Serramonte Boulevard||Southbound exit and northbound entrance|
|R25.28||47B||South end of SR 1 overlap; signed as exit 47 northbound|
|R25.78||48||Eastmoor Avenue, Mission Street||Signed as exit 47 northbound|
|M27.17||49A||Daly City, Westlake District (Junipero Serra Boulevard)||Signed as exit 49 southbound|
|M27.17||49B||North end of SR 1 overlap; northbound left exit and southbound entrance|
|R0.74||50||Southbound exit and northbound entrance|
|R1.77||51||Geneva Avenue, Ocean Avenue|
|R2.70||52||Monterey Boulevard||Southbound exit and northbound entrance|
|R2.70||52||San Jose Avenue||Northbound exit and southbound entrance|
|R3.28||53||Alemany Boulevard, Mission Street|
|R4.34||54A||Signed as exit 54 southbound|
|R4.34||54B||Northbound exit and southbound entrance|
|R5.62||55||Cesar Chavez Street, 25th Street|
|R6.60||56||Mariposa Street, 18th Street|
|T7.54||57||Sixth Street||Northbound exit and southbound entrance|
|T7.26||King Street||Northbound exit and southbound entrance|