advances in milling iron and machine tools. Together with Simeon North and other armorers, Hall contributed to the adoption of interchangeable parts and the American System as a whole. The men who had learned Hall's methods of interchangeable parts while working at Harper's Ferry went on to apply those methods to production of shoes, watches, clocks, bicycles, clothing, rubber goods, and, later, automobiles. Hall's methods transformed the United States from an economy of workshop craftsmen to a nation of industrialized mass production. Notes External links americanprecision.org Patent on Hall's rifle 1781 births 1841 deaths 19th-century American inventors Firearm designers People of the Industrial Revolution People from Portland, Maine