The Argo Gold Mine & Mill is one of the few remaining preserved mines and mills from Colorado's Gold Rush era.

The 4.16 mile long Argo tunnel (originally the Newhouse Tunnel) opened in 1893 and was finally completed in 1910. It was designed to both connect local mine workings - it was estimated that the tunnel connected to at least 100 mines - which allowed these mines to transport gold and silver ore direct to the mill and the rail head in Idaho Springs as well as providing drainage for them. The latter had been a huge problem for many years. Indeed one writer (Arthur Lakes) noted that, "One mine [in the Central City area ] for years raised on an average 40 tons [36 t] of water for every ton of ore and rock," mined.

In 1913 the Argo Reduction & Ore Purchasing company constructed the mill adjacent to the Argo tunnel portal and mining operations continued in the Argo Tunnel until January 1943 when an effort to reopen a mine ended with a catastrophic disaster that killed four miners and released a tidal wave of water into the town of Idaho Springs beneath the tunnel. To this day the Argo Tunnel continues to discharge heavily contaminated water - nearly 850 pounds of dissolved metals are released from the tunnel each day - and this is treated by the Argo Tunnel Water Treatment Facility in Idaho Springs which came online in April 1998. You can find more information about the history of the mine as well as tour information here: http://argomilltour.com/