Fort Worth is a city in the U.S. state of Texas and the seat of Tarrant County, covering nearly 350 square miles into Denton, Johnson, Par…Fort Worth is a city in the U.S. state of Texas and the seat of Tarrant County, covering nearly 350 square miles into Denton, Johnson, Parker, and Wise counties. According to the 2023 United States census estimate, Fort Worth's population was 978,468, making it the 5th-most populous city in the state and the 12th-most populous in the United States. Fort Worth is the second-largest city in the Dallas–Fort Worth–Arlington metropolitan area, which is the fourth-most populous metropolitan area in the United States, and the most populous in Texas.