Fort Worth is the 15th-largest city in the United States and the fifth-largest city in the state of Texas. It is the county seat of Tarrant County, covering nearly 350 square miles (910 km2) into four other counties: Denton, Johnson, Parker and Wise. According to the 2017 census estimates, Fort Worth's population is 874,168. The city is the second-largest in the Dallas–Fort Worth–Arlington metropolitan area, which is the 4th most populous metropolitan area in the United States. Fort Worth was established in 1849 as an army outpost on a bluff overlooking the Trinity River. Fort Worth has historically been a center of the longhorn cattle trade. It still embraces its Western heritage and traditional architecture and design.