Salt was a valuable commodity, and an industry developed near salt springs in the Ohio River Valley, producing salt by evaporating brine from the springs. Salt wells were sunk at the salt springs to increase the supply of brine for evaporation. Some of the wells were hand-dug, but salt producers also learned to drill wells by percussion (cable tool) methods. In a number of locations in western Virginia, Ohio, and Kentucky, oil and natural gas came up the wells along with the brine. The oil was mostly a nuisance, but some salt producers saved it and sold it as illuminating oil or medicine. In some locations, enough natural gas was produced to be used as fuel for the salt evaporating pans. Early salt brine wells that produced byproduct oil included the Thorla-McKee Well of Ohio in 1814, a well near Burkesville, Kentucky, in 1828, and wells at Burning Springs, West Virginia, by 1836.