1907 - Harold Ashford found that several claims by Keys Gold Mining Company had not been assessed as required, and took possession of the claims.
1910 - Discovering that their claims were being mined, Keys Gold Mining took the Ashford brothers to court. The judge ruled in favor of the Ashford brothers.
1910-1914 - The Ashford brothers worked their claims without good results.
1915 - The claim was leased to the McCauslands, who invested over $125,000 in capital improvements, including the mill, 5 miles and 3500 feet below the mine. They soon found that the ore wasn't rich enough to recoup their investment, and ceased operations in September 1915. They also didn't pay their lease payment to the Ashford brothers to cut their losses, and despite winning a lawsuit, the Ashfords never received payment.
1926 - After sitting idle for years, four men were working the mine for a short period.
1935 - Leased to Golden Treasure Mines who did not use the outdated mill, instead shipping the ore to the railroad in Shoshone.
1938 - Golden Treasure Mines ceased their operations of the mine, so the Ashfords continued themselves for a short period.
1941 - After working the mine for a brief period, the Ashfords leased the mine to Bernard Granville and Associates, who after making additional improvements to the mine, ceased operations without apparently ever shipping any ore.
It appears that the mill was last used in 1915 and the mines have been idle since 1941.
information source: http://www.nps.gov/history/history/online_books/deva/section4c5.htm