The southernmost point of I-5 is at the Mexican border at the San Ysidro Port of Entry, one of the busiest border crossings 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 Chula Vista and National City 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, and passing the I-805 merge (where it becomes the widest Interstate in the United States for a short stretch), before passing through several North County coastal suburbs and then through of Marine Corps Base Camp Pendleton in northern San Diego County. Here I-5 is also known as the San Diego Freeway.