Pouring forth millions of gallons of clear, icy water daily, these springs feed the San Marcos River and the 1,380-square-mile area it drains. The immense springs rise at the Balcones Escarpment, a geologic fault line that cuts across the state and separates upland from lowland Texas. Their abundant fresh water drew the Indians who inhabited Central Texas and later the European explorers and settlers who followed. The Alonso de Leon Expedition first gave the name San Marcos to a Texas river on April 26, 1689, Saint Mark's Day, though the name was not applied to the present river until 1709. Other explorers visited the area, and in 1755 it became a temporary site for several Spanish missions. Almost a century later, in 1845, pioneers William W. Moon and Mike Sessom made a permanent settlement here. In 1851 Gen. Edward Burleson, William Lindsey, and Eli T. Merriman bought adjacent land and laid out the town of San Marcos. Drawn by the area's scenic beauty, A. B. Rogers started a park here in 1926, and over the years it was developed into Aquarena Springs, one of Central Texas' most popular tourist attractions.