San Juan County, Washington was established on October 31, 1873 and named for the San Juan Islands, so called by Spanish explorer, Francisco de Eliza, in 1791! Its county seat is Friday Harbor, and its fair is also held in Friday Harbor! You might recognize San Juan Island National Historical Park, San Juan Islands National Monument, Roche Harbor, and the Patos Island & Lime Kiln Light Stations, which are located in this county!