Brownsville is a city in and the county seat of Cameron County, Texas, United States. Brownsville is the 15th largest city in the state of Texas and the 129th largest in the United States. The population was 139,722 at the 2000 census. Brownsville is also the southernmost city in Texas. Brownsville is the principal city of the Brownsville–Harlingen Metropolitan Statistical Area, which is part of the larger Brownsville–Harlingen–Raymondville Combined Statistical Area.