On March 5, 1895, Wyoming entered the refining business when Philip "Mark" Shannon and his partners opened the state's first oil refinery near Casper, Wyoming. The small but ambitious facility was capable of processing about 100 barrels per day, producing lubricants that ranged from light cylinder oil to heavy industrial grease.
At the time, Wyoming was still a sparsely populated frontier, with fewer than 100,000 residents statewide, yet demand for lubricants was growing rapidly due to railroads, mining operations, and agricultural machinery across the Rocky Mountain region. The refinery helped reduce reliance on imported petroleum products from distant states.
This early operation laid the groundwork for Wyoming's future as a major energy producer. Just a few years later, large discoveries such as the Salt Creek Oil Field would transform the state into one of America's most important crude-oil suppliers, making this modest refinery a key first step in Wyoming's oil history.
