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.
450px|thumb|Peak of [[Mount Ellinor in the Olympic Mountains of Mason County]]
Geography
thumb|[[Mount Rainier over the Totten Inlet Mason County, Washington]]
According to the United States Census Bureau, the county has a total area of , of which is land and (8.7%) is water.
Geographic features
- Brown Cove
- Case Inlet
- Hammersley Inlet
- Harstine Island
- Hood Canal
- Lake Cushman
- Mason Lake
- Olympic Mountains
- Puget Sound
- Squaxin Island
- Totten Inlet
Oakland Bay
Major highways
- 23px U.S. 101
- 20px SR 3
- 20px SR 108
- 20px SR 106
Adjacent counties
- Jefferson County – northwest
- Kitsap County – northeast
- Pierce County – east/southeast
- Thurston County – southeast
- Grays Harbor County – southwest
National protected areas
- Olympic National Forest (part)
- Olympic National Park (part)