Stillwater is the tenth-largest city in the U.S. state of Oklahoma, and the county seat of Payne County. It is located in north-central Oklahoma at the intersection of U.S. Route 177 and State Highway 51. As of the 2020 census, the city population was 48,394. The Stillwater Micropolitan Statistical Area had a population of 78,399 according to the 2012 census estimate. Stillwater was part of the first Oklahoma Land Run held on April 22, 1889, when the Unassigned Lands were opened for settlement and became the core of the new Oklahoma Territory. The city charter was adopted on August 24, 1889, and the city operates under a council-manager government system.