The Treadwell Mine Historic Trail was once the site of the most productive gold mine in the United States, with $70 million of gold removed by 2,000 miners; Of the 144 buildings that existed in Treadwell in 1910, only a few foundations remain, and the new office building is the only one remaining. When you visit this landmark, you'll be able to see the remains of buildings and old mining machinery, as well as a pit where the mine collapsed during a heavy rain in 1917.