Automobiles, also called cars, are self-propelled motor vehicles designed to transport people. Most definitions specify that automobiles run primarily on roads, seat one to eight people, have four wheels and are constructed mainly to carry cargo (as opposed to trucks, which are designed primarily for the transportation of goods). The modern automobile evolved during the nineteenth century from early steam-powered road vehicles built by French inventor Nicolas-Joseph Cugnot in 1769, to internal combustion engines. American businessman Henry Ford is credited with revolutionizing automotive manufacturing in the early 20th century by developing assembly lines. These techniques allowed him to produce millions of his Model T automobiles, lowering their cost until they became affordable for most middle-class families.

The automobile has had a significant impact on the economy, society and culture of the United States. It has led to the development of new industries and services, such as car dealerships, repair shops and service stations. It has encouraged participation in outdoor recreational activities and prompted the creation of travel-related businesses, such as airlines, hotels and tour companies. The automobile has ended rural isolation and brought urban amenities–most importantly, better medical care and schools–to rural America. It has increased the use of oil and other fossil fuels, causing the need for environmental controls and increased monitoring of air quality. It has stimulated urban growth and industrialization, as well as suburban residential development, and it has brought new jobs and wealth to many Americans.

Cars have become an essential part of life in the United States, with most people owning one or more. The automobile has helped bring women into the workforce, making it possible for them to have careers and personal freedom. It has also given them the opportunity to vote, and paved the way for equal rights for women in society.

Modern cars are more comfortable and safer than ever before, with features such as air conditioning, power steering and windows, and heated seats and mirrors. Many have advanced safety systems, including airbags and backup cameras to help prevent accidents. The automotive industry is constantly developing and upgrading its products to keep up with consumer demand.

In addition, the design and construction of an automobile depends to a large degree on its intended use. For example, off-road automobiles need simple systems with high resistance to severe overloads and extreme operating conditions, while products that will be used on limited-access highway systems require improved passenger comfort options, optimized engine performance and handling, and high-speed stability. The body of the vehicle, which includes the front and rear bumpers, spoilers and doors, is an important component as it determines the size and shape of the automobile. This is also where all of the systems are housed, such as the transmission, differential and a variety of sensors. The braking system is another vital component, as it ensures that the automobile can stop safely in the event of an accident or an emergency situation. This is where the brakes, rotor and calipers are located.