In the 1970s, Smith made a large contribution to our understanding of how interchangeability of mechanical parts went from concept to realization. He did this by rescuing from obscurity the work of gunmaker John Hall at the Harpers Ferry Armory. During 1815–1834, Hall had assembled elements of standardization and combined it with new machine designs and effective team management to realize the long-desired goal of true parts interchangeability. Hall's innovative breechloading US Rifle Model 1819 was the first product ever made in large numbers whose components could be freely exchanged with one another and still function. Earlier industrial historians had often credited Eli Whitney with perfecting standardized parts, but although Whitney did make some progress toward the goal, he ultimately gave up the effort. Smith's research on Hall's work at Harpers Ferry has put the Maine craftsman back in his proper position in the industrial pantheon. (David Hounshell, From the American System to Mass Production, 1800-1932, p. 29.) Hall's manufacturing technique became known as the American System, and today it is widespread. "Although recognized by his contemporaries as a major contributor to the American System," wrote industrial historian David Hounshell in 1984, "John H. Hall escaped the attention of modern historians until recently. Merritt Roe Smith's Harpers Ferry and the New Technology has provided an outstanding study of Hall's achievements." (Hounshell, American System, p. 39.)
