In the 1920s, farmers and irrigators in Idaho worked to muster support from the U.S. Department of Interior to build a dam and impoundment on the Fall River, pictured here, to give them more water for growing crops. It would have come at a huge ecological cost to the southwest corner of Yellowstone, also known as the "Cascade Corner" because of its abundance of waterfalls. It also would have affected wildlife habitat and angling. It was almost built. Photo courtesy NPS