King County is a county located in the U.S. state of Washington. The population was 2,269,675 in the 2020 census, making it the most populous county in Washington, and the 12th-most populous in the United States. The county seat is Seattle, also the state's most populous city.
Originally named after US representative, senator, and then vice president-elect William R. King in 1852, the county government amended its designation in 1986 to honor Martin Luther King Jr., a prominent activist and leader during the civil rights movement. The change was approved by the state government in 2005.