Kittitas County // is a county located in the U.S. state of Washington. As of the 2010 census, the population was 40,915. 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'. Most anthropologists and historians concede that each interpretation has some validity depending upon the particular dialect spoken."
Kittitas County officially separated from Yakima County in 1884.