Laguna Atascosa National Wildlife Refuge is the largest protected area of natural habitat left in the Lower Rio Grande Valley. The 120,000-acre (49,000 ha) refuge is located almost entirely in Cameron County, Texas, 25 mi (40 km) east of Harlingen, although a very small part of its northernmost point extends into southern Willacy County.

The Lower Rio Grande Valley, commonly known as the Rio Grande Valley or locally as the Valley or RGV, is a region spanning the border of Texas and Mexico located in a floodplain of the Rio Grande near its mouth. The region includes the southernmost tip of South Texas and a portion of northern Tamaulipas, Mexico. It consists of the Brownsville, Harlingen, Weslaco, Pharr, McAllen, Edinburg, Mission, San Juan, and Rio Grande City metropolitan areas in the United States and the Matamoros, Río Bravo, and Reynosa metropolitan areas in Mexico. The area is generally bilingual in English and Spanish, with a fair amount of Spanglish due to the region's diverse history and transborder agglomerations. It is home to some of the poorest cities in the nation, as well as many unincorporated, persistent poverty communities called colonias. A large seasonal influx occurs of "winter Texans" — people who come down from the north for the winter and then return north before summer arrives.