<P> A number of innovations were either invented or improved sufficiently to allow for mass production during the decade: air conditioning, automatic transmission, power steering, power brakes, seat belts and arguably the most influential change in automotive history, the overhead - valve V8 engine . The horsepower race had begun, laying the foundation for the muscle car era . </P> <P> Automobile manufacturing became the largest industry segment in the US, and the largest ever created; the US auto industry was many times larger than the automotive industries of the rest of the world combined . By 1960, one - sixth of working Americans were employed directly or indirectly by the industry, but automation and imports eroded the need for such a large workforce within a couple of decades . The 1950s were the pinnacle of American automotive manufacturing and helped shape the United States into an economic superpower . </P> <P> At least 100 automobile companies had begun operations in Detroit by the beginning of the 20th century, but by the 1920s, the decade that gave rise to the Big Three, Ford was the largest . </P> <P> In American automobile parlance, the Big Three refers to General Motors (GM), Ford and Chrysler, each of which had bought out other companies to become conglomerates earlier in the 20th century . Together they accounted for 70 percent of auto sales . Their combined market share grew over the following decades, declining only slightly after World War II, but the Big Three soon came to dominate the industry, claiming 94 percent of all automobile sales in 1955, 1956 and 1959 . The industry grew at a pace never before seen, and the broader industry soon employed one - sixth of the entire American workforce . </P>

What were cars in the 1950s made of