Leechburg is a borough in southern Armstrong County, Pennsylvania, United States, 35 miles (56 km) northeast of Pittsburgh. Leechburg was founded by David Leech, for whom it was later named, and was incorporated as a borough in 1850. Located along the Kiskiminetas River, Leechburg was known as a major port of the Pennsylvania Canal. Early in the twentieth century, it had been the site of extensive steel sheet works, foundries, cement plants, and productive coal mines. Leechburg was the first place where natural gas was used for industrial purposes.