Longview is a city in Cowlitz County, Washington, United States. It is the principal city of the "Longview, Washington Metropolitan Statistical Area", which encompasses all of Cowlitz County. Longview's population was 36,648 at the time of the 2010 census and it is the largest city in Cowlitz County. The city is located in southwestern Washington, at the junction of the Cowlitz and Columbia rivers. Longview shares a border with Kelso to the east, which is the county seat.