In 1874, during the Black Hills Expedition led by Lieutenant Colonel George Armstrong Custer, the discovery of gold in the region sparked the Black Hills Gold Rush. As prospectors located valuable sources of gold along Deadwood and Whitewood Creeks, thousands more prospectors entered the area looking to stake their claim. In April, 1876, a gold outcropping was discovered near Lead, South Dakota. This gold claim became the Homestake Mine and was the primary source of the placer gold being mined from the surrounding area. Over the next century, ten percent of the world's gold supply would come from this site.