Alamo, located in the Rio Grande Valley is a city in the irrigated area of southern Hidalgo County, Texas, United States in an area of vegetab…Alamo, located in the Rio Grande Valley is a city in the irrigated area of southern Hidalgo County, Texas, United States in an area of vegetable farming and citrus groves, and is a noted winter resort/retirement town near the Mexico–U.S. border. Alamo is one of the Rio Grande Valley's gateways to Mexico, via U.S. Route 281 and Nuevo Progreso, Tamaulipas, as well as a gateway to the Santa Ana National Wildlife Refuge. Alamo's population was 19,493 at the 2020 census.