Big Bend Ranch State Park in southwestern Brewster County and southeastern Presidio County is the largest park in the state system; it comprised more than 299,000 acres in 2004. At one time the Big Bend Ranch was among the ten biggest working ranches in Texas. The first known ranchers in the area were Andrés Madrid, who began running sheep north of the site of present Lajitas in the 1870s, and the Carrasco family. In the 1910s the brothers Woodworth, Gus, and Gallie Bogel began buying and consolidating small stock outfits in the vicinity; they went bankrupt during the Great Depression, however, and their holdings were purchased by Mannie and Edwin Fowlkes, who continued the process of consolidation begun by the Bogels.
The property changed hands several more times before Robert O. Anderson, chairman of Atlantic Richfield Corporation, offered it to the state for $8 million, or about $36 an acre. The price was well under market value, but land commissioner Robert Armstrong could not persuade the legislature to approve the sale at that time. A few years later Governor William Clements attempted to arrange a land-swap deal whereby Anderson would receive state lands elsewhere in exchange for the ranch, but the plan was defeated amid charges of cronyism. In 1986 Anderson announced that he would sell oil leases on eighty-six acres of Big Bend Ranch, but on July 21, 1988, the Texas Parks and Wildlife Commission formally approved the purchase of the ranch by the state for $8.8 million. The title to the ranch was at that time held by the Hondo Oil and Gas Company, owned by Anderson and Walter Mischer of Houston.
The site was opened to the public on January 19, 1991, as the Big Bend Ranch State Natural Area; in 1995 the site was redesignated as the Big Bend Ranch State Park. Visitor centers have been constructed near each end of the park: at Fort Leaton State Historic Site, four miles southeast of Presidio, and at the Barton Warnock Environmental Education Center, just east of Lajitas. The two are connected by Ranch Road 170, known as the Camino del Río, which winds some sixty miles between Lajitas and Presidio. The natural area encompasses a vent crater of the defunct Bofecillos Volcano; a collapsed volcanic laccolith along its eastern boundary; picnic tables at Madera Canyon; Colorado Canyon, popular with rafters and canoeists; the thirty-mile unimproved Rancherías Canyon–Leon (Panther) Canyon Trail; a one-half mile trail into Cloud Canyon; one unimproved primitive campground; and all-day guided bus tours from both visitor centers. An additional thirty-two miles of multiuse trails were opened in 2003.
The area has been declared an international biosphere reserve, a nature area recognized under a United Nations program, by the United States government. It is home to eleven endangered species of plants and animals and ninety major archeological sites. Vegetation in the area, of the Chihuahuan Desert variety, includes grama, silver bluestem, tanglehead, and tobosa grasses; mesquite, acacia, creosote, mariola, lechuguilla, ocotillo, and candelilla bushes; scrub oak, cottonwood, ash, willow, and the endangered Hinckley's oak; and the Big Bend or Harvard bluebonnet. Almost 400 species of birds either live in or migrate to the area; the Western mastiff bat, cactus wren, zone-tailed hawk, white-winged dove, great blue heron, beaver, golden eagle, peregrine falcon, deer, mountain lion, javelina, canyon tree frog, Couch's spadefoot toad, Trans-Pecos copperhead, monarch butterfly, Chihuahuan horse-lubber grasshopper, and tarantula belong to the local fauna.