Interstate 5 (abbreviate I-5) is the main Interstate highway on the West Coast of the United States, paralleling the Pacific Ocean from Washington to California and serving some of the largest cities of the western part of the country, including Seattle, Portland, Oregon, Sacramento, Los Angeles and San Diego. Its odd number indicates that it is a north-south highway. Its southern terminus is at the international border between the United States and Mexico in the San Diego community of San Ysidro, California. Its northern terminus is at the international border between the United States and Canada at the Peace Arch in Blaine, Washington. I-5 is the only Interstate highway to touch both the Canadian and Mexican borders. At its southern end, I-5 continues into adjacent Tijuana as Mexico Federal Highway 1. On its north side, I-5 continues into Vancouver, Canada as Highway 99.