Arlington is a principal city in the U.S. state of Texas, located in TarrantCounty. It is part of the Mid-Cities region of the DallasFort WorthArlington metropolitan area, approximately 12 miles (19km) east of downtown Fort Worth and 20 miles (32km) west of downtownDallas. According to the U.S. Census Bureau's estimate, the city had a population of almost 379,577 at the end of 2013, making it the third-largest municipality in the metropolitan area. Arlington is the fiftieth-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 doctoral-granting research institution, the Arlington Assembly plant used by General Motors, the Nuclear Regulatory Commission Region IV, Texas Health Resources, and American Mensa. Additionally, Arlington hosts the Texas Rangers'Globe Life Park in Arlington, and the Dallas Cowboys at the AT&T Stadium, the International Bowling Campus (which houses the United States Bowling Congress, International Bowling Museum and the International Bowling Hall of Fame), and the theme parksSix Flags Over Texas (the original Six Flags) and Hurricane Harbor. Arlington borders Kennedale, Grand Prairie, Mansfield and Fort Worth, and surrounds the smaller communities of Dalworthington Gardens and Pantego.