Automobiles, also known as motor cars, are four-wheeled vehicles designed primarily for passenger transportation and powered by an internal combustion engine using a volatile fuel. They are complex technical systems consisting of several semi-independent subsystems with specific design functions. The modern automobile is a highly integrated system whose design and manufacture draws on breakthroughs in a wide range of technologies.

The scientific and technical building blocks of the automobile date back several hundred years. In the late 1600s Dutch scientist Christiaan Huygens invented a type of internal combustion engine that was sparked by gunpowder; the automobile in its present form, however, only took off around 1900, when Gottlieb Daimler and Karl Benz produced the first truly modern motor car. Early cars used steam, electric power, or gasoline; all had serious drawbacks. Steam engines were expensive to operate, required lengthy warm-up periods, and were slow; electric cars were not suited for highway travel, and gasoline was a dangerous and inconvenient fuel.

Throughout the twentieth century, the automobile has profoundly changed American society. It has provided a means for individuals to move rapidly long distances, reshaping the economy by allowing for the flexible distribution of goods. At the same time it has contributed to suburban sprawl, degrading the countryside and imposing traffic congestion on urban areas. It has also become the main source of pollution in many cities and a major drain on dwindling world oil supplies.

The automobile has fueled economic growth in the United States, where it ranks first in terms of value-added and is one of the largest users of industrial products. It has been a driving force in a new consumer goods-oriented society, and it has transformed the economies of ancillary industries such as steel and petroleum. It has also helped to create a broader middle class by enabling more people to afford to buy and operate cars.

In addition to providing mobility and convenience, the automobile has impacted cultural life. It has contributed to a change in the lifestyle of Americans, with families moving out of urban centers and into the suburbs; people taking vacations by car instead of flying; and musical styles being transformed by the popularity of rock and roll music, which can be heard on AM radio stations as well as on the FM dial.

Although the automobile has revolutionized society, its own technology is now being surpassed by new forces. The automobile is undergoing a transition into an Age of Electronics, with the use of such devices as the personal computer and the laser becoming more commonplace. In this new age, it is likely that the car will become less important. For most Americans, however, the automobile remains a vital means of transportation and an integral part of their daily lives. This is reflected in the fact that more than 90 percent of households own at least one vehicle, and almost half own more than one. The average American drives over three trillion miles (almost five trillion kilometers) each year.