I-5

Interstate 5 in Washington (I-5) is a highway in the U.S. state of Washington that extends from its border with Oregon to its border with Canada. Serving the cities of Vancouver, Kelso, Chehalis, Centralia, Tumwater, Olympia, Tacoma, Seattle, Everett, Mount Vernon, and Bellingham, it is the main route between Portland, Oregon, and Vancouver, British Columbia. It is the only interstate to traverse the whole north–south length of Washington, but the undivided highways U.S. Route 97 and U.S. Route 395 do also. I-5 is also the only north–south primary interstate highway in Washington. The road is the busiest in the state; an estimated 240,000 motorists use the road daily. The second busiest is I-405 at 201,000.