Interstate 8

Interstate 8
Interstate 8 highlighted in red
Route information
Length:	350.34 mi (563.82 km) 171.98 miles (276.77 km) in California 178.36 miles (287.04 km) in Arizona
Existed:	1964 – present
Major junctions
West end:	Sunset Cliffs Boulevard / Nimitz Boulevard in San Diego, CA
	I-5 in San Diego, CA I-805 in San Diego, CA I-15 / SR 15 in San Diego, CA SR 111 in El Centro, CA US 95 in Yuma, AZ SR 85 in Gila Bend, AZ
East end:	I-10 in Casa Grande, AZ
Location
States:	California, Arizona
Counties:	CA: San Diego, Imperial AZ: Yuma, Maricopa, Pinal
Highway system
Interstate Highway System Main Auxiliary Suffixed Business State highways in California Interstate U.S. State Pre-1964 History Unconstructed Deleted Freeway Scenic Arizona Highways Interstate U.S. State Unconstructed Former ← SR 7 CA SR 9 → ← SR 802 AZ I-10 →

Interstate 8 (I-8) is an Interstate Highway in the southwestern United States. It runs from the southern edge of Mission Bay at Sunset Cliffs Boulevard, in San Diego, California, almost at the Pacific Ocean, to the junction with I-10, just southeast of Casa Grande, Arizona. In California, the freeway travels through the San Diego metropolitan area as the Ocean Beach Freeway and the Mission Valley Freeway before traversing the Cuyamaca Mountains and providing access through the Imperial Valley, including the city of El Centro. Crossing the Colorado River into Arizona, I-8 continues through the city of Yuma across the Sonoran Desert to Casa Grande, in between the cities of Phoenix and Tucson.

The first route over the Cuyamaca Mountains was dedicated in 1912, and a plank road served as the first road across the Imperial Valley to Yuma; east of there, the Gila Trail continued east to Gila Bend. These were later replaced by U.S. Route 80 (US 80) across California and part of Arizona, and Arizona State Route 84 (SR 84) between Gila Bend and Casa Grande. The US 80 freeway through San Diego was largely complete by the time it was renumbered as I-8 in the 1964 state highway renumbering; east of San Diego, the US 80 roadway was slowly replaced by I-8 as construction progressed in the Imperial Valley. The Arizona portion of the road was built starting in the 1960s. Several controversies erupted during the construction process; questionable labor practices in Imperial County led to the federal conviction of mobster Jimmy Fratianno, and the Arizona government was found to have mismanaged financial resources by the U.S. House of Representatives subcommittee.