what county is ellensburg in
City of Ellensburg. Ellensburg is a city in, and the county seat of, Kittitas County, Washington, United States. The population was 18,174 at the 2010 census. Ellensburg is located just east of the Cascade Range on Interstate 90 and is known as the most centrally located city in the state. Ellensburg is the home of Central Washington University (CWU).