Trains are huge, heavy, and important modes of transportation. Before automobiles, they were the main mode of motorized transportation and helped many people move west to places like New Mexico. They also carried building materials, household goods, food, and other products faster and cheaper to locations across the United States. A train includes locomotives that move it, a cab where the engineer sits and runs the train, an end-of-train device that electronically monitors brake line pressure and accidental separation of train cars, and couplers that connect the cars. Freight trains move cargo such as cotton, corn, automobiles, coal, and many other products from one place to another, and most trains carry cargo while a few carry people. In 1814, George Stephenson designed the first steam locomotive, and the steam engine's use of fire, water, and steam to move the wheels made trains a popular mode of transportation.