Hueco Tanks is an area of low mountains and historic site in El Paso County, Texas, in the United States.

Hueco is a Spanish word meaning hollows and refers to the many water-holding depressions in the boulders and rock faces throughout the region.

Due to the unique concentration of historic artifacts, plants and wildlife, the site is under protection of Texas law; it is a crime to remove, alter, or destroy them.

The park consists of three syenite (a weak form of granite) mountains; it is 860 acres (350 ha) in area[3] and is popular for recreation such as birdwatching and bouldering.

[4] Hueco Tanks State Park & Historic Site was obtained from the county by special deed on June 12, 1969, and by purchase of 121 acres (49 ha) additional land on August 10, 1970.

This 860.3 acres (348.2 ha) park is named for the large natural rock basins or "huecos" that have furnished a supply of trapped rainwater to dwellers and travelers in this arid region of west Texas for millennia.

The inscribed names of Texas Rangers and US Cavalrymen, as well as Native American artifacts and paintings, attest to its historic nature.

By about 700 years ago, the population of the village could no longer be sustained by the small agricultural area surrounding Hueco Tanks.

"[13] In 1837, the Kiowa signed a treaty with the United States, however, shortly after Mexican soldiers forced them into a six-day siege in Hueco Tanks, during which most of them died.

[14] The ranch went on the real estate market in 1956 and during this time, members of archaeological and historical societies raised awareness of the area's significance.

[21] The first scientific overview of the rock paintings at Hueco Tanks happened in the summer of 1939 with Forrest and Lula Kirkland recording the art.

The pluton was eventually exposed through weathering to form the rock formations visible today, which jut from the desert floor.

Hueco Tanks contains the single largest concentration of mask paintings by Native Americans in North America, of which hundreds exist at this site.

[28] Freshwater shrimp and spadefoot toads survive at the site; for this and other reasons, visitors are cautioned against touching the pools of water at Hueco Tanks to avoid destroying the eggs of these animals.

Other trees found in the area include netleaf hackberry, Texas mulberry, Mexican buckeye, catclaw acacia, and Arizona white oak.

[26] Hueco Tanks is widely regarded as one of the best areas in the world for bouldering,[33] that is, rock climbing low enough to attempt without ropes for protection.

In any given climbing season, which generally lasts from October through March, it is common for climbers from across Europe, Asia, and Australia to visit the park.

Only North Mountain is accessible without guides, and then only for about 70 people at any given time, except on the south side at ground level, which is closed to the public.