The first full scale working steam locomotive was Richard Trevithick's Coalbrookdale locomotive. It was constructed for Coalbrookdale ironworks in Shropshire, England, though no record of it working there has survived.

On February 21, 1804, the first recorded steam hauled railway journey took place as Trevithick's locomotive hauled a train from the Pen-y-darren ironworks, near Merther Tydfil, to Abercynon in South Wales.

Accompanied by Andrew Vivian, a fellow engineer, it ran with mixed success. The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency.

Stephenson's Rocket of 1829 was a huge improvement, as it was, strong, fast, reliable, and efficient. After it won the Rainhill trials, other early railways looked towards Robert Stephenson and Co. for steam locomotives.

The first locomotive to operate in the United States was the Stourbridge Lion, built in 1829 by Foster, Rastrick and Co. for the Delaware and Hudson Canal Company. It was taken to Honesdale, PA and tested on D&H's new track, performing well, but found to be too heavy for the track. The project was abandoned, and over the next few decades it was dismantled until only the boiler remained.

Steam locomotives are classified by wheel arrangement, known as Whyte notation. Whyte notation counts the number of wheels on a locomotive, for example, a 4-6-2. This means, from left to right, the front of the locomotive has four leading wheels, on two axles, six drivers on three axles, and 2 trailing wheels on one axle. Basically, take the number of axles and multiply by two.

Steam locomotives from the beginning were built on a fire-tube basis, with the cab built around the firebox, smokebox and chimney at the front. The engineer was in charge of the throttle, which regulated how much steam was sent into the cylinders to drive the locomotive.

The throttling device itself is located in a steam dome, a slight extension off the top of the boiler, where steam is regulated towards the cylinders. In the early 1900s, superheaters were just coming into use, passing through boiler tubes or over the firebox, and into the cylinders.

This increased the efficiency of locomotives, as well as the capabilities. Pictured is an english 4-6-2, with detailing of the exhaust blastpipe, valving of the cylinder, and Walschaerts valve gear. Safety valves can be seen behind a shroud just in front of the cab, which release steam at a set pressure, one a few pounds below the boilers capability, and another several pounds below that one, above an optimal operating pressure.

Enclosures were built around the rear of the boiler, where the Engineer (operator of the locomotive) and Fireman (in charge of firing the locomotive) tended their duties. As locomotives became capable of higher speeds, and weather naturally becomes inclement, the crew needed this cab for protection from the elements, and for comfort for long trips.

Locomotives in America usually have some sort of Pilot, or Cow Catcher on the front of the locomotive in the event of animals or debris on the track. A headlight is almost always on, and two ditch lights are used nowadays for visibility, or to flash back and forth as a visible warning.

In the 1940's and 50's, a Mars light was used on diesel and some steam locomotives. It was a beacon that oscillated in a figure 8 in addition to a headlight, that was used as a visible warning to motorists at night. The bell and whistle are used for safety as well as communication.

In the United States, the bell is used when a locomotive is starting, stopping, and at low speeds. The whistle signals movement, and a warning when crossing roads. Two short blasts indicate forward movement about to start. One is used when halting, and three for reverse.

When a locomotive with or without train approach a crossing, two longs, a short and a long signal the approach, the last signal ending on top of the crossing. These are common signals still used today. Trains have come a long ways in brakes as well. In the old days, a hand brake on the locomotive stopped the train, and later, each car had its own brake as well.

In 1869, George Westinghouse invented the air brake, and the automatic air brake in 1872. Each car of the train has a valve and a cylinder, and the cylinder is connected to each car, and the locomotive, which has a compressor and a valve. When the air is released in the locomotive, all brakes on the train set at the same time.

A water injector, or gun, is standard equipment on any locomotive. Old style link and pin couplings were dangerous for coupling and uncoupling trains, and it wasn't uncommon for brakemen to have lost fingers. The Janney coupler was designed in 1873, and can be controlled by a rod on each side of the train.

The first diesel locomotives started appearing in the 1920's and 30's, and their capabilities were seen early on, with the speed and power of Burlington's Pioneer Zephyr. It ran between Denver, CO and Chicago, IL in 13 hours 5 minutes, averaging 77 MPH.

Diesel locomotives were fast, efficient, and easier to maintain. But steam was well established, and it took until 1960 for the last class 1 railroad to dieselize. With the release of EMDs FTs around 1939, the end of steam came ever closer.