In 1798 Eli Whitney signed a contract to deliver “ten thousand stands of arms by September 30, 1800.” In January 1801 he showed his muskets to President John Adams and President-elect Thomas Jefferson. Jefferson wrote that Whitney “has invented moulds and machines for making all the pieces of his locks so exactly equal.”
Whitney finished the contract in January 1809. The historian Merritt Roe Smith concluded that “Whitney must have staged his famous 1801 demonstration with specimens specially prepared for the occasion.” The parts of surviving Whitney muskets “were not even approximately interchangeable.”
Interchangeable parts were achieved later by others, among them Simeon North and John Hall. The method became known as the “American system of manufacturing.”