Brutal competition was a hallmark of the business throughout the 20th century. In 1926 the United States had no fewer than 43 carmakers, the high point. The fastest rising among them was General Motors, whose marketing strategy was to produce vehicles in a number of distinct styles and price ranges, the exact opposite of Henry Ford's road to riches. GM further energized the market with the concept of an annual model change, and the company grew into a veritable empire, gobbling up prodigious amounts of steel, rubber and other raw materials, and manufacturing components such as spark plugs and gears in corporate subsidiaries.

As the auto giants waged a war of big numbers, some carmakers sold exclusivity. Packard was one. Said a 1930s advertisement: "The Packard owner, however high his station, mentions his car with a certain satisfaction—knowing that his choice proclaims discriminating taste as well as a sound judgment of fine things." Such a car had to be well engineered, of course, and the Packard more than met that standard. So did the lovingly crafted Rolls-Royce from Great Britain and the legendary Maybach Zeppelin of Germany, a 1930s masterpiece that had a huge 12-cylinder engine and a gearbox with eight forward and four reverse gears. (The Maybach marque would be revived by Mercedes seven decades later for a car with a 550-horsepower V12 engine, ultra-advanced audio and video equipment, precious interior veneers, and a price tag over $300,000.)

At the other extreme was the humble, economical Volkswagen—literally, "people's car"—designed by engineer Ferdinand Porsche. World War II delayed its production, but it became a runaway worldwide hit in the 1950s and 1960s, eventually eclipsing the Model T's record of 15 million vehicles sold. Japan, a leader in the development of fuel-efficient engines and an enthusiastic subscriber to advanced manufacturing techniques, also became a major global player, the biggest in the world by 1980.

The automobile's crucial role in shaping the modern world is apparent everywhere. During the 19th century, suburbs tended to grow in a radial pattern dictated by trolley lines; the car has allowed them to spring up anywhere within commuting distance of the workplace—frequently another suburb. Malls, factories, schools, fast-food restaurants, gas stations, motels, and a thousand other sorts of waystops and destinations have spread out across the land with the ever-expanding road network. Taxis, synchronized traffic lights, and parking lots sustain modern cities. Today's version of daily life would be unthinkable without the personal mobility afforded by wheels and the internal combustion engine.

Not surprisingly, the automobile remains an engineering work in progress, with action on many fronts, much of it prompted by government regulation and societal pressures. Concerns about safety have put seatbelts and airbags in cars, led to computerized braking systems, and—on the cutting edge of technology—fostered interest in devices that can enhance night vision or warn of impending collisions. Onboard microprocessors reduce polluting emissions and maximize fuel efficiency by controlling the fuel-air ratio. New materials—improved steels, aluminum, plastics, and composites—save weight and may add structural strength.

As for the motive power, engineers are working hard on designs that complement or may someday even supplant the internal combustion engine. One avenue of research involves electric motors whose power is generated by fuel cells that draw electrical energy from an abundant substance such as hydrogen. Already at hand are hybrid cars, powered by both gasoline and electricity. Unlike all-electric cars, hybrids don't have to be plugged in to be recharged; instead, their battery is charged by either the gasoline engine or the electric motor acting as a generator when the car slows. Finally, manufacturing has seen an ongoing revolution that would dazzle even Henry Ford, with computers greatly shortening the time needed to design and test a car, and regiments of industrial robots doing machining and assembly work with a degree of speed, strength, precision, and endurance that no human can match.

Back in 1923 a national magazine declared that the automobile had "outrun the dreamers, confounded the prophets, and amazed the world." True enough—and that was just the beginning.