The Homestake Mine in neighbouring Lead (pronounced "leed"), four miles up the road from Deadwood, was the largest and deepest gold mine in North America. It opened in 1876 during the gold rush and didn't close until 2002, producing more than forty million ounces of gold and reaching a depth of nearly 8,000 feet.
The Sanford Lab Homestake Visitor Center on Main Street in Lead has an open-pit overlook the size of several football stadiums and exhibits on both the mining history and the underground physics laboratory that now occupies the lower tunnels. It is one of the more unusual pairings of industrial heritage and pure-science research anywhere in the world.