Jefferson County is located in the northern portion of Washington State’s Olympic Peninsula. It is bordered on the west by the Pacific Ocean, the north by Clallam County, the northeast by the Strait of Juan de Fuca, the east by the waters of the Hood Canal and Admiralty Inlet, the southwest by Grays Harbor County and the southeast by Mason County. As of the 2010 U.S. Census, Jefferson County had total land area of 1,803.70 square miles and a population of 29,872. Port Townsend is its largest city with a population of 9,113. Also of interest:
- The intersecting watershed sub-basins(7): Hoh-Quillayute, Queets-Quinalt, Lower Chehalis, Dungeness-Elwha, Hood Canal, Puget Sound and Skokomish.
- Major lake: Leland Lake
- Major rivers: Hoh River, Queets River, Clearwater River, Dukabush River, Dosewallips River, Little Quilcene River, Quinault River and Solleks River.
- Mount Olympus (7,980 feet) is highest peak in the Olympic Mountains and the central feature of the Olympic National Park.