For over 30 years, the Jackson Ferry Shot Tower manufactured ammunition for a growing nation and, according to research and tax records, became the first factory to mass-produce shot on American soil. English immigrant Thomas Jackson came to the United States through Baltimore to answer a call from Moses Austin, who was hiring experts in mining and lead works. Jackson, an industrialist and experienced miner, brought with him the trade secret of drop shot, a process refined by craftsman William Watts of Bristol, England. The tower took over five years to build and was completed in 1807. It produced shotgun ammunition, particularly fowling shot, for local communities, and manufacturing ceased in 1839. In the drop shot process, workers hoisted lead to the top by block and tackle using livestock, ropes, and pulleys; smelted the lead and added arsenic; poured the molten lead through giant sizing sieves; and let it fall through the tower into a kettle of water at the bottom, where the water cushioned the shot rather than cooled it. The shot was then retrieved, dried, polished with graphite, and sold on site or shipped downriver to nearby towns. The tower stands 75 feet tall, with a central shaft extending another 75 feet into the ground for a total drop of 150 feet, the height needed to form a perfect round ball. An access tunnel at the river base once allowed workers to retrieve shot from the bottom of the shaft, but the Norfolk and Western Rail Road Co. collapsed the tunnel when it brought the rail line through to prevent a potential catastrophe.