A group of Euro-Americans discovered salt springs in July, 1877 near the future town sites of Newcastle and Cambria. In November of 1878, James LeGraves started mining the salt and shipping it to the Black Hills gold mines. LeGraves erected a furnace that contained two evaporating pans, which he used to collect the salt. LeGraves sent the salt to the Black Hills by freight wagon, where it was used in chlorinating the extracted gold and silver. He prospered for the next six years. When the railroad reached Rapid City, it brought a cheaper supply of salt, at the same time LeGraves' equipment began to wear. As a result, LeGraves ended his salt mining business in 1884.
The salt springs remained out of production while commercial coal mining began in 1887, which led to the establishment of Cambria a few miles from the springs. By 1905 the Cambria coal mines were in full production and a new group, the Cambria Salt Company organized to process the 35,000 pounds of salt produced every 24 hours from the nearby springs. Cambria Salt laid a pipeline three and one-half miles to Cambria, where the salt mining plant was located. The company sold the salt to the coal companies as well as shipped it to the Black Hills. Wanting to expand, and insure its future, the company drilled to find the salt bed. The Cambria Salt Company never found it,
and after considerable investment, in 1909 it sold the property, ending attempts to produce salt from the Cambria Salt Mine.