Interstate 5 California Descriptions

The most southerly point of Interstate 5 is at the United States-Mexico border at the San Ysidro border crossing, one of the busiest in the world. Beginning at the border in San Ysidro, which is part of the city of San Diego, as the John J. Montgomery Freeway, I-5 goes through the suburbs of National City and Chula Vista before reaching downtown San Diego. It then parallels the Pacific coastline, going through the northern suburbs of San Diego, bisecting the University of California, San Diego campus, before passing through the 28 miles (45 km) of Marine Corps Base Camp Pendleton in northern San Diego County. Here I-5 is also known as the San Diego Freeway.

At Dana Point, I-5 turns inland and heads due north through Mission Viejo to the El Toro Y interchange in southeastern Irvine. I-5 becomes the Santa Ana Freeway as it runs southeast to northwest, passing through major cities and suburbs in Orange and Southern Los Angeles counties. Angelenos refer to it as "the 5" or as the Santa Ana Freeway. From this point, the San Diego Freeway continues northward as I-405.

When the freeway reaches the East Los Angeles Interchange one mile (1.6 km) east of downtown Los Angeles, I-5 becomes the Golden State Freeway. The route continues through the San Fernando Valley and then crosses the Newhall Pass through the Santa Susana Mountains into the Santa Clarita Valley. For about a four-mile (6 km) stretch between Santa Clarita Valley and the Pyramid Lake, the northbound and southbound lanes separate and actually invert, with the southbound lanes being to the east of the northbound ones. Beginning at that point, the Golden State Freeway sharply rises to the north through the Grapevine to eventually reach the second-highest point of its entire length, the Tejon Pass (elevation 4,183 ft. (1,275 m)) through the Tehachapi Mountains. Path 26 power lines generally parallel the freeway along this stretch. The freeway then sharply descends for 12 miles (19 km) at Tejon Pass to around 1,600 feet (488 m) at Grapevine near the southernmost point of the San Joaquin Valley, approximately 30 miles (50 km) south of Bakersfield and 4 miles (6 km) south from where State Route 99 splits away from it in Wheeler Ridge.

I-5 south approaching Weed and Mt. Shasta.From Highway 99 to south of Tracy, I-5 skirts along the far more remote western edge of the great Central Valley, and thus here is removed from population centers such as Bakersfield and Fresno with other state highways providing connections. Interstate 580 splits off from I-5 at a point south of Tracy, providing a loop-route connection to the San Francisco Bay Area. After passing Tracy, I-5 heads due north through Stockton and Sacramento before turning due west to Woodland. At Woodland, the interstate heads northwest again towards Dunnigan, where it converges with Interstate 505.

From Dunnigan, I-5 skirts north along the western edge of the Sacramento Valley to Red Bluff. I-5 then enters the Shasta Cascade region, passing through Redding and Shasta Lake before climbing up to near the foot of Mount Shasta. The interstate then travels to Weed and Yreka before reaching the Oregon border.