King County is 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 13th-most populous in the United States. The county seat is Seattle, also the state's most populous city.

King County is represented in the United States Congress through a near-entirety of the population in the 7th and 9th Congressional Districts, a majority of the population in the 8th Congressional District and a plurality of the population in the 1st Congressional District. In the state legislature, King contains the entirety of the 5th, 11th, 33rd, 34th, 36th, 37th, 41st, 43rd, 45th, 46th, 47th, and 48th legislative districts as well as the near-entirety of the 30th legislative district, about one-half of the 32nd legislative district, about one-third of the 1st and 31st legislative district, and a mere 627 people in the 39th legislative district. The only legislative districts represented by Republicans that include any part of King County are the 31st and 39th districts.[citation needed]

The people of King County voted on September 5, 1911, to create a Port District. King County's Port of Seattle was established as the first Port District in Washington State. The Port of Seattle is King County's only Port District. It is governed by five Port Commissioners, who are elected countywide and serve four-year terms. The Port of Seattle owns and operates many properties on behalf of King County's citizens, including Sea-Tac International Airport; many seaport facilities around Elliott Bay, including its original property, publicly owned Fishermen's Terminal, home to the North Pacific fishing fleet and the largest homeport for fishermen in the U.S. West Coast;[citation needed] four container ship terminals; two cruise ship terminals; the largest grain export terminal in the U.S. Pacific Northwest; three public marinas; 22 public parks; and nearly 5,000 acres of industrial lands in the Ballard-Interbay and Lower Duwamish industrial centers.