Big Bend National Park, a unit of the National Park System. It is in southwestern Texas in an area where the Rio Grande makes a 90-degree bend, for which the park was named. Big Bend occupies 1,158 square miles (2,999 km2). The park has desert and mountain terrain, and a number of deep, rocky canyons. Cacti and other desert plants are the prevalent vegetation; forests, mainly coniferous, occur in the higher parts of the Chisos and Sierra del Carmen mountains. The park was authorized by Congress in 1935 and was established in 1944.