The Washington Mine, nestled in the northern Shawangunk mountains, was first operated in 1863 by the Washington Mining Company. The company discovered a small deposit of galena and sphalerite trending northeast. Three adits were driven to crosscut the vein at various points. Above the uppermost adit, the ore was worked from the surface and followed downward to meet the tunnel. It is believed the vein pinched as it dipped northwest.

The mine operated very briefly before closing in 1864. In 1906, the mine was reopened and operated by the Phoenix Lead Company of Paterson, NJ. However, the mine was only worked until 1907 when it was permanently abandoned. Despite considerable exploratory effort, no ore was ever shipped.