Interstate 90 in Washington

Interstate 90
Interstate 90 is highlighted in red
Route information
Maintained by WSDOT
Length:	296.92 mi (477.85 km)
Tourist routes:	Mountains to Sound Greenway - I-90
Major junctions
West end:	I‑5 / SR 519 in Seattle
	I‑405 in Bellevue I‑82 / US 97 near Ellensburg US 395 near Ritzville US 2 in Spokane US 195 in Spokane
East end:	I-90 at Idaho state line
Location
Counties:	King, Kittitas, Grant, Adams, Lincoln, Spokane
Highway system
Interstate Highway System Main Auxiliary Suffixed Business State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← I‑82 SR 92 →

Interstate 90 (I-90), a transcontinental Interstate Highway from Seattle, Washington, to Boston, Massachusetts, crosses the state of Washington before crossing the Idaho state line between Spokane and Post Falls. It serves the cities of Seattle, Bellevue, Issaquah, Ellensburg, Moses Lake, Ritzville, and Spokane.

It is the only Interstate Highway to cross the state east to west, but there are two U.S. Routes that also do the same, U.S. Route 2 and U.S. Route 12, along with a few state highways. I-90 is also the only highway in Washington to connect the two largest cities in the state (Seattle and Spokane). The road is the third busiest in the state, behind I-5 at 240,000 and I-405 at 201,000. An estimated 148,000 motorists use the road daily.