The Silver King Mine traces its beginning to 1870, during the Apache Wars. General George Stoneman, desiring an easier access route to Apache strongholds, had ordered the construction of a road from Camp Picketpost into the Pinal Mountains. The road became known as the Stoneman Grade. A soldier named Sullivan, who was assigned to the construction, discovered some heavy black rocks that flattened when struck. Interested in the rock, he collected several samples but did not mention this to his fellow soldiers. After completing his term of service, Sullivan went to work on a ranch owned by Charles Mason. Sullivan routinely showed off the rocks, known as nugget silver to prospectors of the region, but never divulged the location of the discovery. After a time, Sullivan disappeared and was assumed to have been killed by Apache.