For the Texas State Park see Big Bend Ranch State Park.
Big Bend National Park is an American national park located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topography and ecology in the United States. The park protects more than 1,200 species of plants, more than 450 species of birds, 56 species of reptiles, and 75 species of mammals.
Geological features in the park include sea fossils and dinosaur bones, as well as volcanic dikes. The area has a rich cultural history, from archeological sites dating back nearly 10,000 years to more recent pioneers, ranchers, and miners.
The park encompasses an area of 801,163 acres (1,251.8 sq mi; 3,242.2 km2). For more than 1,000 miles (1,600 km), the Rio Grande/Río Bravo forms the boundary between Mexico and the United States, and Big Bend National Park administers approximately 118 miles (190 km) along that boundary. The park was named after a large bend in the river, and the Texas—Mexico border.
Because the Rio Grande serves as an international boundary, the park faces unusual constraints while administering and enforcing park rules, regulations, and policies. In accordance with the Treaty of Guadalupe Hidalgo, the park's territory extends only to the center of the deepest river channel as the river flowed in 1848. The rest of the land south of that channel, and the river, lies within Mexican territory. The park is bordered by the protected areas of Parque Nacional Cañon de Santa Elena and Maderas del Carmen in Mexico.