Del Rio was originally settled by Spanish missionaries who arrived on St. Phillip's Day, 1635, and named their mission San Felipe del Rio. But archaeological evidence suggests that the area around Del Rio, in particular, the canyons of the Rio Grande and Pecos River, have been inhabited for at least 12,000 years. Indian pictographs that remain on canyon walls are at least 4,000 years old.
The Indians who resided in the area when the Spanish arrived were probably Coahuiltecans; whoever they were, they didn't submit to missionization and the San Felipe mission was short lived. The Coahuiltecans mysteriously disappeared sometime during the 18th century and the area was abandoned until the 1850s when Fort Clark was established in nearby Brackettville to protect the San Antonio-El Paso Trail. As the area became "pacified", Anglo-American speculators became interested in the land around San Felipe Springs, which then, as now, pumped around 100 million gallons of water a day out of the rocky ground. The springs were an important water stop for stagecoaches on the San Antonio-San Diego route (which connected with the Chihuahua Trail as well) and for the U.S. Camel Corps during their Big Bend surveys.
A Fort Clark cavalry post called Camp del Rio was established nearby in 1876 and by the mid-1880s was abandoned along with Fort Clark, as the Indian Wars came to a close. Del Rio finally began to grow as a town in 1883 when the railroad ran through the area.
As Del Rio is on the edge of the Edwards Plateau - an environment perfect for cloven-hoofed livestock - sheep and goats ranchers moved in and the town has become a major contender for the nation's "wool and mohair capital" title along with San Angelo farther north. Another boon to Del Rio development was the building of the Amistad International Dam in the 1960s, which created one of the largest man-made laked in the U.S. (by impounding the Rio Grande, Pecos River, and Devils River), with nearly a thousand miles of shoreline. The latest development has been the establishment of more than 30 maquiladoras or "twin plants", American-owned factories located in or near Acuna on the Mexican side, which has helped to expand Del Rio's population to its current 35,000.
Another claim to fame for Del Rio-Acuna is that two famous radio personalities broadcasted from a "pirate" radio station on the Mexican side, XER. The first was Dr. John R Brinkley, the infamous goat gland surgeon of the 30s; the second was rock-'n'-roll DJ Wolfman Jack in the late 50s and early 60s. The facility was set up so that announcers could operate out of a Del Rio studio while the 500,000 watt transmitter (with a signal that reached all the way to Canada) was actually located in Acuna, thus circumventing FCC licensing. Mexican radio still rules the airwaves in this part of Texas.