About thirty million years ago, volcanic plumes of syenite porphyry, a type of granite, pushed up through beds of sedimentary rock, remnants of an inland sea that had covered West Texas hundreds of millions of years earlier. The sedimentary stone has gradually eroded in the area, leaving hills up to 450 feet tall that rise from the otherwise flat landscape of the desert basin between the Franklin Mountains and the Hueco Mountains. The hills take their name from the Spanish word for hollow ( hueco) eroded basins in the rock that retain rainwater. There are several basins, one large enough to form a year-round lake, which had the only drinkable water between the Pecos River and El Paso in this area before the twentieth century. This water supported an oak and juniper woodland like that found in the Davis and Guadalupe Mountains, along with deer and other prey animals.
The earliest evidence of habitation dates back more than 10,000 years, when hunting bands searched the hills for Ice Age animals. Later, smaller hunter-gatherer groups used the area, and agriculture was introduced about 1,000 CE. A village of semi-subterranean, wattle-and-daub houses dating from c. 1100 lasted more than one hundred years. From the sixteenth through the nineteenth centuries, Mescalero and Lipán Apache, Jumano, and Tigua bands camped in the area.
More than 5,000 pictographs and petro glyphs have been found at Hueco Tanks, left by peoples from the oldest to the most recent times. Near the visitor-accessible areas, much of the rock has recently been defaced. The ruins of a relay station for the Butterfield Overland Mail (which carried mail and passengers from St. Louis to California between 1858 and 1861) stand near the park’s entrance. In 1898, after Silverio Escontrias and his wife, Pilar, acquired the land for a cattle and horse ranch, they built an adobe house, which is now the park’s interpretive center.