Arlington is a city in Tarrant County, Texas, United States. It is part of the Mid-Cities region of the Dallas–Fort Worth–Arlington metropolitan statistical area, and is a principal city of the metropolis and region. The city had a population of 398,431 in 2020, making it the second-largest city in the county after Fort Worth and the third-largest city in the metropolitan area, after Dallas and Fort Worth. Arlington is the 50th-most populous city in the United States, the seventh-most populous city in the state of Texas, and the largest city in the state that is not a county seat. Arlington is home to the University of Texas at Arlington, a major urban research university, the Arlington Assembly plant used by General Motors, the Nuclear Regulatory Commission Region IV, Texas Health Resources, Mensa International, and D. R. Horton. Additionally, Arlington hosts the Texas Rangers at Globe Life Field, the Dallas Cowboys at AT&T Stadium, the Arlington Renegades at Choctaw Stadium, the Dallas Wings at College Park Center, the International Bowling Campus (which houses the United States Bowling Congress, International Bowling Museum and the International Bowling Hall of Fame), and the theme parks Six Flags Over Texas (the original Six Flags) and Hurricane Harbor.