While Pennsylvania was once a major player in the American salt industry, it does not currently have active, large-scale commercial salt mines like those found in New York or Ohio. Historically, however, the state was a leader in salt production. In the early 1800s, Western Pennsylvania—specifically the Conemaugh and Allegheny Valleys—was the third-largest salt producer in the country. Instead of "mining" solid rock salt, these early operations used a "salt well" method, where they bored hundreds of feet into the ground to reach saltwater springs (brine). This brine was then pumped to the surface and boiled in large furnaces to create high-quality table salt. Interestingly, this salt-drilling history is what led to the Pennsylvania oil boom; when salt drillers like Samuel Kier found "dark, greasy liquid" (petroleum) contaminating their salt wells, they eventually realized the oil was more valuable than the salt. Today, there is still salt deep beneath the state in the Salina Group of rock formations, but it is not economically viable to mine compared to the massive salt mines in the surrounding states that supply the region's road salt.