Chelan County is a county in the U.S. state of Washington. As of the 2010 census, its population was 72,453. The county seat and largest city is Wenatchee. The county was created out of Okanogan and Kittitas Counties on March 13, 1899. It derives its name from a Chelan Indian word meaning "deep water," likely a reference to -long Lake Chelan, which reaches a maximum depth of 1,486 feet (453 m).