[Not to be confused with Keystone in White Pine County]

Keystone was a small company camp established by the Old Dominion Mining Company in 1868, soon home to fifty residents and two saloons. That first incarnation of Keystone was short lived, and the Keystone Mine operated only periodically until 1881. That February, the Florence or Rattlesnake District was formed, and several mines attracted miners to Keystone. This renewed interest too faded, and by 1885 Keystone was abandoned.

A rich silver discovery was made by J.H. Hillyer in December 1910, and soon the Hot Creek Development Company began working the old claims. Ore was processed until 1926 at a mill originally built during the late part of the 19th century. Beginning in late 1926, the MacNamara Mining & Milling Company began shipping ore to the Treadwell-Yukon Mill at Tybo. This activity came to a close in the early 1930s (though the old Keystone Mill was refurbished in 1930).

Keystone remained vacant for several decades, but in the late 1970s a cyanide leaching operation began treating the old tailings, lasting into the early 1980s. In 1990, another brief leaching operation was undertaken by Nevada Goldfields, Inc. The district has remained idle since, and some stone ruins remain (though the old mill was leveled for the recent leaching operations).