The Iron Horse commemorative bill celebrates that most fascinating of self-propelled vehicles, the locomotive, a common feature on American landscapes for generations. Experimental steam locomotives were first built in Wales and England in 1803. The first U.S. steam locomotive was built by John Stevens in 1825, and the first commercially usable locomotive, the Tom Thumb, was built by Peter Cooper in Baltimore in 1830. Improvements through the years eventually enabled a locomotive to move up to 200 freight cars at 75 mph (120 kph). Steam from wood or coal fuel was the main source of power until the mid-20th century, though electric power had been used from the early 20th century in Europe. After World War II diesel power replaced steam because of its higher efficiency and lower cost, though diesel-electric and gas turbine-electric combinations were also used. Many songs have been written about locomotives and trains, and many folklore stories involve trains. Get your hands on these choo-choo, err, Iron Horse Train bills today!