Isaac Pennock, regarded as the founder of the business that became the Lukens Steel Company, began manufacturing iron in the early 1790s when he erected a mill called the Federal Slitting Mill at Rokeby on Buck Run in Chester County, about four miles south of Coatesville. The operation produced blacksmith iron, barrel staves, and miscellaneous iron products. In 1816, Dr. Charles Lukens, Pennock's son-in-law, entered the ironmaking business, and he is remembered for rolling the first boiler plate in America in 1818, setting the company's course as a specialty plate producer. After Dr. Lukens died in 1825, his widow Rebecca ran the mill. The plates were made from single charcoal blooms formed in an old-fashioned forge fire, reheated over an ordinary grate fire, and then rolled into plates or sheets. The plate rolls were about 16 to 18 inches in diameter and 3 to 4 feet long, driven by an overshot water wheel. As demand for Lukens plate increased and greater power was needed, the overshot water wheel was replaced by a breast wheel, a flywheel was introduced, and larger rolls measuring 21 inches in diameter and 66 inches in length were adopted.