Big Bend National Park, 801,163 acres (324,471 hectares), W Tex.; authorized 1935, est. 1944. It is a triangle formed where the Rio Grande runs southeast then northeast in a big bend along the U.S.-Mexico border, notably through deep canyons such as the Santa Elena. The river, the Chihuahan desert plain, and the Chisos Mts. offer sharp contrasts in wilderness scenery. The park has petrified trees, vestiges of prehistoric cultures, and rare forms of animal and plant life. See National Parks and Monuments (table). One hundred miles (160 km) to the west is Big Bend Ranch State Park, the largest Texas state park, established in 1988 and covering 287,000 acres (116,200 hectares).