Automobiles are vehicles used for passenger transportation. They usually have four wheels, and are propelled by internal combustion engines using a volatile fuel. They are one of the most universal modern technologies, and are one of the most widely used consumer goods on Earth.

In the 1920s automobiles became the backbone of a new consumer-goods-oriented society. Cars brought urban amenities, such as schools, hospitals and recreation opportunities, to rural America. They enabled people to work and play at a greater pace than possible before, and they created a variety of related industries such as roadside services, motels, restaurants, and gas stations. They also fueled the growth of other industrial sectors, such as steel and petroleum.

While the technological building blocks of the modern automobile were established in the late 1600s, it wasn’t until 1914 that the industry was able to produce enough cars for mass market consumption. Early cars were powered by steam, electricity or gasoline. Steam engines could drive at high speeds, but they had a limited range and were difficult to start. Electric cars were easy to operate but often had problems with power loss and recharging stations. Gasoline was the most efficient and convenient of these three sources.

By the 1930s, market saturation coincided with technological stagnation: The basic design of post-World War II automobiles remained basically the same as the Model T’s, except for more advanced features such as self-starters and closed all-steel bodies. During World War II, automobile makers focused on producing for the war effort. After the war, concerns about nonfunctional styling, safety and fuel economy rose, as did questions about air pollution and the drain on dwindling world oil reserves.