For more than 1,000 miles (1600 km), the Rio Grande / Río Bravo forms the international boundary between Mexico and the United States, and Big Bend National Park administers approximately 244 miles (393 km) along that boundary.

Big Bend National Park has national significance as the largest protected area of Chihuahuan Desert topography and ecology in the United States, which includes more than 1,200 species of plants, more than 450 species of birds, 56 species of reptiles, and 75 species of mammals. The park covers 801,163 acres (3,242 km2). Few areas exceed the park's value for the protection and study of geologic and paleontologic resources. Cretaceous and Tertiary fossil organisms exist in variety and abundance. Archeologists have discovered artifacts estimated to be 9,000 years old, and historic buildings and landscapes offer graphic illustration of life along the international border in the 1800's.

Because the Rio Grande serves as an international boundary, the park faces unusual constraints when administering and enforcing park rules, regulations, and policies. In accordance with the Treaty of Guadalupe Hidalgo, the park has jurisdiction 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.

Geography and climate
The park exhibits dramatic contrasts; its climate may be characterized as one of extremes. Dry and hot late spring and summer days often exceed 100 °F (38 °C) in the lower elevations. Winters are normally mild throughout the park, but sub-freezing temperatures occasionally occur. Because of the range in altitude from approximately 1,800 feet (550 m) along the river to Emory Peak in the Chisos Mountains at 7,832 feet (2,387 m). A wide variation in available moisture and in temperature exists throughout the park. These variations contribute to an exceptional diversity in plant and animal habitats. Some species in the park, such as the Chisos, are found nowhere else in the United States.

The 118 miles (190 km) of river that form the southern park boundary include the spectacular canyons of Santa Elena, Mariscal, and Boquillas. The Rio Grande, meandering through this portion of the Chihuahuan Desert, has cut deep canyons with nearly vertical walls through three uplifts comprised primarily of limestone. Throughout the open desert areas, the highly productive Rio Grande riparian zone includes numerous plant and animal species and significant cultural resources. The vegetative belt extends into the desert along creeks and arroyos.

South of the border lie the Mexican states of Chihuahua and Coahuila and the new protected areas for flora and fauna, which are regions known as the Maderas del Carmen and the Cañón de Santa Elena.

(The above is found on Wikipedia, the free encyclopedia.)

This book depicts photographs taken while visiting Big Bend National Park.