Interstate 8 is the main east-west Interstate highway serving the San Diego metropolitan area. It begins at the foot of the San Diego River at Sunset Cliffs Boulevard, and it leads east into Arizona. For most of its route, Interstate 8 replaces U.S. 80, which used to extend all the way to San Diego rather than its current terminus in Dallas.
The following is a synopsis of the history of Interstate 8 in the San Diego metropolitan area:
1954. U.S. 80 routed along El Cajon Boulevard and Washington Street through the City of San Diego. U.S. 80 merges with the new Cabrillo Freeway (Old U.S. 395/California 163) at the Washington Street-Cabrillo Freeway interchange.
Around 1957. Construction began on U.S. 80 freeway between U.S. 395 (California 163) and Ward Road (Future Interstate 15) and Mission Gorge Road.
1958. Six-lane U.S. 80 freeway completed between 70th Street and Baltimore Avenue, with plans to extend the highway to the Grossmont Summit and California 67 (now California 125).
1958-1959. Contract let to construct U.S. 80 freeway between U.S. 101 (Pacific Highway, now Interstate 5) and U.S. 395 (California 163) at a projected cost of $1,214,000 for 1.3 miles of eight-lane freeway. Due to the rapid rise of motels in this section of Mission Valley, land prices begin to climb.
1959. With rights-of-way acquisition completed, construction is underway for U.S. 80 freeway between Chase and Magnolia Avenues.
1959-1960. The Grossmont Summit section of the U.S. 80 freeway is completed at a cost of $3,594,000 between La Mesa Boulevard and Chase Avenue in El Cajon. This segment includes one section with 18 lanes side-by-side, which was unprecedented in the early 1960s. At the same time, the budget for Fiscal Year 1960 includes appropriation for the 2.32-mile section between Baltimore Drive and La Mesa Boulevard.
Early 1960s. Most sections of U.S. 80 freeway are completed between U.S. 101 and the City of El Cajon. The Alvarado Canyon section of U.S. 80, 2.6 miles of six-lane freeway between Waring Drive and Lake Murray Drive (70th Street), replaced a City arterial street. The City planned that Alvarado Canyon Road would be replaced with a freeway, so it acquired much of the necessary rights-of-way (ROW) through this stretch.
1962. Business U.S. 80 routed along El Cajon Boulevard (old U.S. 80) according to 1962 Texaco map of San Diego.
1964. Great Renumbering of 1964. U.S. 80 freeway is officially renamed to Interstate 8, although U.S. 80 signs would remain along the freeway until 1972. A 1966 Mobil Map illustrates Interstate 8 and U.S. 80 as cosigned along the Mission Valley and Alvarado Freeways.
1967. Business U.S. 80 (El Cajon Boulevard) now known as Business Loop I-8 between U.S. 395 freeway and La Mesa. The now-constructed Ocean Beach Freeway is shown on a 1967 Thomas Brothers Guide as California 109, a designation that went away by 1971.
1971. Interstate 8 extended west to meet Sunset Cliffs and Nimitz Boulevards over California 109 (the Ocean Beach Freeway). Some maps still carried the California 109 designation over this freeway as late as 1975, but most maps showed this route as part of Interstate 8 in 1971.
1972. Last vestiges of U.S. 80 are removed from the Interstate 8 freeway.
1975. Interstate 8 freeway completed as far east as Pine Valley.
1996. Asphalt freeway between California 163 and Interstate 5 rehabilitated.
1997-1998. Concrete freeway rehabilitated from the City of El Cajon east to California 163. This was accomplished by removing a thin layer of concrete off the top of the roadway, which promoted a smoother, quieter freeway.
January 1999. Overhead sign for Business Loop I-8 (Washington Street) exit from northbound California 163 removed as part of construction project. It is unlikely that this sign will be replaced.
Summer 1999. New transition ramp constructed from westbound Interstate 8 to southbound California 15.
December 2000. Work continues to expand Interstate 8 by one lane in each direction east of El Cajon.
August 2002. First numbered exit at Hotel Circle (Exit 4A) along eastbound is placed.
