Issaquah is a city in King County, Washington, United States. The population was 30,434 at the 2010 census. According to the Washington State Office of Financial Management, Issaquah ranked 6th of 279 eligible incorporated communities in population growth between 2000 and 2005. Forbes.com ranked Issaquah the 2nd fastest-growing suburb in the state, and the 89th in the nation.