Olympia is the capital of the U.S. state of Washington and the county seat and most populous city of Thurston County. The Squaxin and other Coast Salish peoples inhabited the southern Puget Sound region prior to the arrival of European and American settlers in the 19th century. The Treaty of Medicine Creek was signed in 1854 and followed by the Treaty of Olympia in 1856; these two treaties forced the Squaxin to relocate to an Indian reservation. Olympia was incorporated as a town on January 28, 1859, and as a city in 1882. It had a population of 55,605 at the time of the 2020 census, making it the state of Washington's 23rd most populous city. Olympia borders Lacey to the east and Tumwater to the south.