In 1920, the United Comstock Mines Company was organized by prominent Comstock mining engineers Roy Hardy and Alex Wise with financial backing by New York businessman Harry Payne Whitney. United Comstock consolidated ownership of the entire Gold Hill section of the Comstock Lode, representing 5,000 feet of strike length and a mill site in American Flat. This enterprise constructed the 2,500 ton-per-day capacity American Flat cyanide mill, the largest in the world at the time, and drove a tunnel 9,585 feet from the mill under Gold Hill. The economics of this project were tenuous, and with a drop in silver prices, it closed in 1924.