Interstate 5 (
I-5) is the main
Interstate Highway on the
West Coast of the United States, running largely parallel to the
Pacific coast of the continental U.S. and
U.S. Route 99 from
Mexico to
Canada, through the states of
California,
Oregon and
Washington. It serves some of the largest cities on the U.S. West Coast, including
Seattle,
Portland,
Sacramento,
Los Angeles, and
San Diego, and also links the capital cities of
Washington (
Olympia),
Oregon (
Salem), and
California (
Sacramento) together. The highway's southern terminus is the
Mexico–United States border and its northern terminus is the
Canada–United States border; it is currently the only continuous Interstate highway to touch the U.S. borders with both Canada and Mexico. Upon crossing the Mexican border at its southern terminus, Interstate 5 continues to
Tijuana,
Baja California as
Mexico Federal Highway 1. Upon crossing the Canadian border at its northern terminus, it continues to
Vancouver as
British Columbia Highway 99. It is the 12th longest highway in the U.S. following
Interstate 15 and the 5th longest north-south highway following Interstate 15.