Cowlitz County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 110,730. The county seat is Kelso, and its largest city is Longview. The county was formed in April 1854. Its name derives from the anglicized version of the Cowlitz Indian term Cow-e-liske, meaning either 'river of shifting sands' or 'capturing the medicine spirit.' Cowlitz comprises the Longview, WA Metropolitan statistical area, which is also included in the Portland-Vancouver-Salem, OR-WA Combined statistical area.

Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington state or Washington State to distinguish it from the national capital, both named for George Washington. Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and the Canadian province of British Columbia to the north. The state was formed from the western part of the Washington Territory, which was ceded by the British Empire in the Oregon Treaty of 1846. It was admitted to the Union as the 42nd state in 1889. Olympia is the state capital, and the most populous city is Seattle.