The history of American automobile manufacture began in the early 20th century and has been defined largely by the consolidation of many manufacturers into a few large conglomerates over the course of the 20th century. The development of assembly line production by Henry Ford, the oil crises of the 1970s, and competition from foreign manufacturers in the 1980s and 1990s are also defining features of the history of the American automobile industry.
One of the first American-built automobiles in wide production was the 1901 Oldsmobile built by Ransom E. Olds. Powered by a one-cylinder engine producing 3 horsepower, the Oldsmobile was considered mechanically inferior to the 1901 Mercedes produced by Daimler in Germany but was also significantly less expensive than the German vehicle. However, inefficient production techniques limited the ability of early auto manufacturers to meet demand in the first decade of the 20th century. Henry Ford was one of the major innovators in mass production techniques during this time, with the culmination of his efforts resulting in the concept of the moving assembly line that saw production use in 1914 in the Ford Motor Company's Michigan plant. Other American manufacturers rapidly adopted this model of production.
There were 30 major automobile manufacturers in the United States in the first years of the 20th century, while only the so-called Big Three manufacturers were involved in large-scale American car production by the end. The consolidation of the industry into General Motors, Ford and the Chrysler group resulted from the merger of many brands into single entities during the 1920s and 1930s. Pressure from economic shocks in the 1970s and increasing competition from Japanese manufacturers shuttered most of the few remaining manufacturers and caused an overall decline in the American automotive industry's profitability and productivity toward the end of the 20th century.