streetcar, small, self-propelled railroad car, similar to the type used in rapid-transit systems, that operates on tracks running through city streets and is used to carry passengers. Most often cars of this type are powered by electricity supplied through an underground third rail or an overhead wire. A device called a trolley that is connected to the streetcar's electrical system makes rolling or sliding contact with the rail or wire; hence the name trolley car often is applied to such vehicles. Streetcars are sometimes powered by diesel or other internal-combustion engines, generally in suburban or rural areas, where the distances to be covered make the cost of electrification prohibitive. The first streetcars, which were drawn by horses, were introduced in New York City during the 1830s. The first electric streetcar system for urban passenger service in the United States was introduced in Cleveland during the 1880s. The use of streetcars expanded in the United States until World War I. Since then most have been replaced by buses, although many still remain in use, and a new system of streetcars has been built in San Diego.