⛏ Argo Gold Mine and Mill

The Argo Gold Mine and Mill is a former gold mining and milling property in Idaho Springs, Colorado, featuring an intact gold mill built at the entrance of the Argo Tunnel. The tunnel was built between 1893 and 1910 to drain the gold mines in Virginia Canyon, Gilpin Gulch, Russell Gulch, Quartz Hill, Nevadaville, and Central City and allow easier ore removal. The success of the tunnel as an access route meant that a large volume of ore began exiting at the Idaho Springs entrance and a large mill was built to process it. At the time it was one of the largest such tunnels and milling operations in the world, directly recovering nearly $100 million in gold valued in 2023 at $10.1 trillion. They also sent another $200 million of high-value ores to smelters in Denver.