National Geographic : 1952 Jan
.1 , 129 Santa Fe Railway Water, Slowly Dissolving Limestone, Hollowed New Mexico's Carlsbad Caverns Depositing minerals as it dripped, the water built Twin Dome stalagmites (left) up from the floor of the Big Room. This chamber is 300 feet high, 4,000 feet long, and a maximum 625 feet wide. A National Geographic Society expedition led by Dr. Willis T. Lee in 1924 explored, mapped, and photographed the Carlsbad wonder and made it known to the world. President Coolidge set aside the caverns as a national monument.