BOQUILLAS CANYON. Boquillas Canyon, on the Rio Grande in southeastern Brewster County, is one of the most famous canyons in Big Bend National Park and is a favorite site for float trips down the river. Though its walls are more open and eroded than those in Santa Elena and Mariscal canyons, they still rise as high as 1,500 feet above the river below. They were carved out of thick layers of limestone originally deposited as sediments in a shallow sea, between 60 million and 130 million years ago. The actual length of Boquillas Canyon is a matter of some debate. According to the United States Geological Survey, it begins three miles northeast of the community of Boquillas (at 29°12' N, 102°55' W) and winds four miles east to its mouth five miles northeast of Boquillas (at 29°13' N, 102°53' W). Other estimates put its length at seventeen miles, longer than Santa Elena and Mariscal canyons, and place its endpoint eight miles upstream from Stillwell Crossing just west of the mouth of Heath Creek. The river is somewhat calmer in Boquillas Canyon than in Santa Elena and Mariscal canyons, but Boquillas Canyon is still an imposing sight. M. T. W. Chandler, the leader of a surveying expedition that was to explore the Rio Grande from El Paso to the mouth of the Pecos in 1852, aborted his mission at the canyon, which he called Cañón de Sierra Carmel. Instead, he and his men, their boats wrecked and their supplies low, struck eastward across Mexico to Fort Duncan, near Eagle Pass. Boquillas means "little mouths" in Spanish, perhaps a reference to the canyon's narrow mouth.
Ronnie C. Tyler, The Big Bend (Washington: National Park Service, 1975).