At the Ford Motor Company the assembly line was first adopted in the department that built the Model T's magneto, which generated electricity for the ignition system. Previously, one worker had assembled each magneto from start to finish. Under the new approach, however, each worker performed a single task as the unit traveled past his station on a conveyer belt. "The man who puts in a bolt does not put on the nut," Ford explained. "The man who puts on the nut does not tighten it."

The savings in time and money were so dramatic that the assembly line approach was soon extended to virtually every phase of the manufacturing process. By 1914 the Ford factory resembled an immense river system, with subassemblies taking shape along tributaries and feeding into the main stream, where the chassis moved continuously along rails at a speed of 6 feet per minute. The time needed for the final stage of assembly dropped from more than 12 hours to just 93 minutes. Eventually, new Model Ts would be rolling off the line at rates as high as one every 10 seconds.

So deep-seated was Henry Ford's belief in the value of simplicity and standardization that the Tin Lizzie was the company's only product for 19 years, and for much of that period it was available only in black because black enamel was the paint that dried the fastest. Since Model Ts accounted for half the cars in the world by 1920, Ford saw no need for fundamental change.

Nonetheless, automotive technology was advancing at a rapid clip. Disk brakes arrived on the scene way back in 1902, patented by British engineer Frederick Lanchester. The catalytic converter was invented in France in 1909, and the V8 engine appeared there a year later. One of the biggest improvements of all, especially in the eyes of women, was the self-starter. It was badly needed. All early internal combustion engines were started by turning over the motor with a hand crank, a procedure that required a good deal of strength and, if the motor happened to backfire, could be wickedly dangerous, breaking many an arm with the kick. In 1911, Charles Kettering, a young Ohio engineer and auto hobbyist, found a better way—a starting system that combined a generator, storage battery, and electric motor. It debuted in the Cadillac the following year and spread rapidly from there.

Even an innovation as useful as the self-starter could meet resistance, however. Henry Ford refused to make Kettering's invention standard in the Model T until 1926, although he offered it as an option before that. Sometimes buyers were the ones who balked at novelty. For example, the first truly streamlined car—the 1934 Chrysler Airflow, designed with the help of aeronautical engineers and wind tunnel testing—was a dud in the marketplace because of its unconventional styling. Power steering, patented in the late 1920s by Francis Davis, chief engineer of the Pierce-Arrow Motor Car Company, didn't find its way into passenger cars until 1951. But hesitantly accepted or not, major improvements in the automobile would keep coming as the decades passed. Among the innovations were balloon tires and safety-glass windshields in the 1920s; frontwheel drive, independent front suspension, and efficient automatic transmissions in the 1930s; tubeless and radial tires in the 1940s; electronic fuel injection in the 1960s; and electronic ignition systems in the 1970s. Engineers outside the United States were often in the vanguard of invention, while Americans continued to excel at all of the unseen details of manufacturing, from glass making and paint drying to the stamping of body panels with giant machines.