Brownsville is a city in and the county seat of Cameron County, Texas, United States. Brownsville is the 16th largest city in the state of Texas. Brownsville is the 3rd largest city in the border of Texas with Mexico on the American side. As of April 1, 2010 the population was 175,023 as per the 2010 census. Brownsville is also the southernmost city in Texas and largest by both population and geographic size in the lower Rio Grande Valley.Brownsville is the principal city of the Brownsville–Harlingen Metropolitan Statistical Area, which is part of the larger Brownsville–Harlingen–Raymondville Combined Statistical Area.