Mason County, Washington

Mason County
Mason County Courthouse
Location within the U.S. state of Washington
Washington's location within the U.S.
Coordinates: 47°21′N 123°11′W / 47.35°N 123.18°W / 47.35; -123.18
Country United States
State Washington
FoundedMarch 13, 1854
Named afterCharles H. Mason
SeatShelton
Largest cityShelton
Area
  Total
1,051 sq mi (2,720 km2)
  Land959 sq mi (2,480 km2)
  Water92 sq mi (240 km2)  8.7%
Population
 (2020)
  Total
65,726
  Estimate 
(2024)
69,632
  Density63/sq mi (24/km2)
Time zoneUTC−8 (Pacific)
  Summer (DST)UTC−7 (PDT)
Congressional district6th
Websitemasoncountywa.gov

Mason County is a county located in the U.S. state of Washington. As of the 2020 census, the population was 65,726. The county seat and only incorporated city is Shelton. The county was formed out of Thurston County on March 13, 1854. Originally named Sawamish County, it took its present name in 1864 in honor of Charles H. Mason, the first Secretary of Washington Territory.

Mason County comprises the Shelton micropolitan statistical area and is included in the Seattle-Tacoma combined statistical area.