San Ysidro, San Diego in the context of "Spanish language in California"

There are over 50 places where people may cross the Mexico–United States border. There are also at least eight rail crossings and two ferry crossings along the border. Several large border cities have multiple crossings, often including one or more that bypass the center of the city and are designated for truck traffic. Several crossings have also been closed by the governments of either Mexico or the U.S., or both.

On the U.S. side, the Department of State assigns a three-letter Port of Entry code to each crossing. This code is included on the passport entry stamp or parole stamp one receives when crossing into the U.S. Note that one code may correspond to multiple crossings.

Interstate 5 (I-5) is a major north–south route of the Interstate Highway System in the United States, running largely parallel to the Pacific Coast between the Mexican border and the Canadian border. The segment of I-5 in California runs across the length of the state from the Mexican border at the San Ysidro Port of Entry in the San Ysidro neighborhood of San Diego to the Oregon state line south of the Medford-Ashland metropolitan area. It is the longest interstate in California at 796.77 miles (1,282.28 km), and accounts for more than half of I-5's total length of 1,381.29 miles (2,222.97 km). It is also the second longest stretch of Interstate Highway (and the longest for a north-south Interstate) with a single designation within a single state after I-10 in Texas.

It is the more important and most-used of the two major north–south routes on the Pacific Coast, the other being U.S. Route 101 (US 101), which is primarily coastal. I-5 links the major California cities of San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, and Redding. The San Francisco Bay Area is about 80 miles (130 km) west of the highway.