Steam

The invention of the steam locomotive in 1804 was one of, if not the most important, industrial event of the 19th century. Without it, the Industrial Revolution would have happened much slower than it did, and it's possible that the United States would still be settling it's Western borders. For over 150 years, steam locomotives hauled the majority of the passengers and freight that were moved in the U.S.

The principle of steam locomotion is fairly simple - boil water in an enclosed vessel until it builds pressure, then release that pressure into a chamber with a piston that is attached to axled wheels. The steam pushed the piston, which in turn drives the wheels. Fuel for steam locomotives was plentiful, as they used water, which is in never ending supply, and either coal, wood, or oil as the catalyst to generate heat to boil the water. However, steam locmotives required enormous amounts of maintenance, and it took several hours to get one ready for duty. Add to that the fact that you have to have water stations every few miles to refill the boilers, and you can see that even though it was the best technology for the time, steam locomotives were far from an ideal way to pull trains.

By the 1940's steam locomotives were on their way to extinction. Automobiles and trucks were beginning to get more and more of the passenger and freight business, and airplanes were beginning to come into their own also. The railroads were looking at the new diesel-electic locomotive as a way to reduce crew size, maintenance, and downtime. Both Baldwin and Lima locomotive works built their last steam locomotives in 1949. The last service locomotives were retired in the 1960's.

Today, most steam is relegated to local railroad museums, such as the Tennessee Valley Railroad Museum. Union Pacific is the only major railroad that maintains steam locomotives, and they are only pulled out for display for special excursions.