Kittitas County is a county located in the U.S. state of Washington. As of 2000, the population was 33,362. Its county seat is Ellensburg, which is also the county's largest city. There are numerous interpretations of the name, which is from the language of the Kittitas American Indian language. According to one source, it "has been said to mean everything from 'white chalk' to 'shale rock' to 'shoal people' to 'land of plenty'.