True West Magazine The fabulous Silver King Mine was first discovered in 1873, at a time when conflicts with the Apache Indians were frequent and few people dared prospecting or settling the area. General George Stoneman, setup a camp near the site of frequent Apache raids and ordered the construction of a road into the Pinal Mountains. The road became known as the Stoneman Grade. Sullivan, one of the soldiers working on the road made the discovery of a rich lode of silver. He brought specimens into camp but would not reveal the site of his discovery. Soon after the road was finished, he went to work on a nearby ranch. Eventually Sullivan disappeared and folks figured the Apache had killed him.