A reservoir, Lake Powell, was created by the Glen Canyon Dam. Lake Powell emerged from a struggle over damming Dinosaur National Monument. The Sierra Club and its leader, David Brower, were instrumental in blocking the original site chosen for the dam and they accepted a dam in Glen Canyon. Before the canyon was flooded, Brower floated the canyon and realized what a tremendous resource it was. This experience transformed Brower's attitude towards environmental preservation and the work of the Sierra Club. Photographer Eliot Porter was one of the last photographers to capture the natural beauty of the pre-dam Glen Canyon.