At about that time, North was sent to Captain John H. Hall, superintendent of the federal armory at Harpers Ferry, Virginia (now in West Virginia), to introduce his methods of achieving interchangeability. In 1828, North received a contract to produce 5,000 Hall rifles with parts interchangeable with those produced at Harpers Ferry. North had a 53-year contractual relationship with the United States Department of War. The report of Charles H. Fitch prepared for the 1880 Census, pp. 4,5,26. credits North with a key role in developing manufacture with interchangeable parts.
