During the Industrial Revolution of the 19th century, machines took over most of the manufacturing work from men, and factories replaced craftsmen’s workshops. The event that laid the groundwork for this monumental change was the introduction of interchangeable parts, or pre-manufactured parts that were for all practical purposes identical, into the firearms industry. Interchangeable parts, popularized in America when Eli Whitney used them to assemble muskets in the first years of the 19th century, allowed relatively unskilled workers to produce large numbers of weapons quickly and at lower cost, and made repair and replacement of parts infinitely easier.

Preindustrial Gunmaking

Gunmaking was considered an extremely skilled craft in the 18th century, and firearms, including pistols and muskets, were all constructed by hand. In this way, every gun was a one-of-a-kind possession, and a gun broken could not be easily repaired. At the very least, the process was time consuming and expensive, as the gun had to be brought to a craftsman and repaired to order.

Did you know? Eli Whitney first made his name at the tender age of 27 with his invention of the cotton gin, patented in 1794. This revolutionary device was easily copied, however, and several patent infringement lawsuits gained little to no financial reward for Whitney and his partners.

In the mid-18th century, the French gunsmith Honoré LeBlanc suggested the gun parts be made from standardized patterns, so that all gun parts would follow the same design and could be easily replaced if broken. LeBlanc was not alone in imagining the potential value of this concept; an English naval engineer Samuel Bentham had earlier pioneered the use of uniform parts in the production of wooden pulleys for sailing ships. LeBlanc’s idea didn’t catch on in the French gun market, however, as competing gunsmiths saw clearly the effect that it would have on their craft. In 1789, Thomas Jefferson, then serving as American minister to France, visited LeBlanc’s workshop and was impressed by his methods. Despite LeBlanc’s efforts, however, it would be left to another man to fully introduce interchangeable parts into the American—and later the international—weapons industry.

Eli Whitney’s Impressive Display

In 1797, when Congress voted to prepare the nation for war with France, including the appropriation of a large amount of funds for new weapons, the young inventor Eli Whitney–already known for his invention of the cotton gin in 1794–seized an opportunity to try to make his fortune. In mid-1798, he obtained a government contract to manufacture 10,000 muskets within an extraordinarily short time frame of less than two years.

By January 1801, Whitney had failed to produce a single one of the promised weapons, and was called to Washington to justify his use of Treasury funds before a group that included outgoing president John Adams and Jefferson, now the president-elect. As the story goes, Whitney put on a display for the group, assembling muskets before their eyes by choosing (seemingly at random) from a supply of parts he brought with him. The performance earned Whitney widespread renown and renewed federal support. It was later proven, however, that Whitney’s demonstration was a fake, and that he had marked the parts beforehand and they were not exactly interchangeable. Still, Whitney received credit for what Jefferson claimed was the dawn of the machine age.

The Impact of Interchangeable Parts

Whitney proved to be an effective businessman and manager, dividing labor efficiently among his largely unskilled work force and building precision equipment that enabled the production of large numbers of identical parts quickly and at a relatively low cost. The last of the 10,000 muskets that Whitney had promised in his original contract came in eight years late, but were judged to be of superior quality, and he produced 15,000 more within the next four years.