Steam locomotives run on fire, fuel, and water. Large amounts of water are taken on at the station, along with coal, wood, or oil. The fuel is heated in a firebox to create high-pressure steam. The steam fuels the engine, which drives the wheels. The release of excess steam is what makes the choo-choo-choo-choo sound. This old steam locomotive was built in 1908 and is still running in Nilgiri, India. (MR/ Shutterstock) Read More