When the steam locomotive came into use, nearly all wheeled vehicles were pulled by horses, mules or oxen—mostly horses. The locomotive was looked upon as a sort of mechanical horse; hence, it was popularly called the "Iron Horse," just as in later years the first automobiles were commonly called "horseless carriages." Today we do not often call the locomotive an "iron horse," nor do we call the engine-house or roundhouse in which locomotives are kept a stable, but the places in the roundhouse where the locomotives are kept are still called "stalls," and the roundhouse men who look after the locomotives and take them in and out of their "stalls" are still called "hostlers."

When a locomotive finishes its run, it is usually taken to an engine terminal. At the terminal is the roundhouse, where engines are cleaned and given light or "running" repairs, and made ready for their next runs. The engine terminal also includes a coaling station, a water tank, a sand house, an oil house and an ash pit.

On its arrival at the engine terminal, the engine is taken to the coaling station to be refueled. Its tank is filled with water from a tank or column. The sand dome on top of the boiler is filled with dry sand from the heated sand house. Then, the engine is moved to the ash pit where the fire-grates are cleaned and ashes and cinders are removed from under the firebox.

If the engine requires further attention to put it in condition for the next run, it is taken to the roundhouse. Some engine terminals have two or three roundhouses, others have only one; some roundhouses have many stalls; others have only a few, depending upon the number of engines to be serviced.

The roundhouse is a sort of locomotive garage. Its name is derived from its shape. Many roundhouses are semi-circular in shape, many others form a complete circle except for one or two openings for entrance and exit tracks.

Each locomotive stall is fitted with large doors on the inner side. There are windows above the doors and also on the outer side. Each stall bears a number, as shown in the picture.

Long pits between the tracks in the stalls permit inspection and repair of locomotives from underneath.

Adjacent to or in the roundhouse is a machine and blacksmith shop. There are also rooms for storing supplies, a tool house, lockers for the workmen, and a small office for the master mechanic or foreman in charge of the roundhouse.

One of the most interesting features of the roundhouse is the turntable, by which locomotives are turned so as to enter or leave the stalls, or by which locomotives may be turned around.

(Trains, locomotives and cars can also be turned around on wye tracks, i.e., two tracks leading off from another track, forming a junction and ending in a single track like the letter Y.)

The turntable is pivoted at the center and is supported at the ends by wheels which run on a circular track. From the turntable, tracks spread out fanwise.

When the engine is in position on the turntable, as shown in the picture, the operator moves the turntable slowly, by means of an electric or gasoline motor, to a track leading to an empty stall or to the terminal yard. Small turntables are sometimes moved by hand. Steam locomotives with tenders measure from 60 to 90 feet or more in length. Turntables must be built to accommodate the heaviest and longest locomotives employed on the railroad, or at least on the local division of the railroad. The locomotive in the picture is one of the largest in the country. Its huge size can be seen from the size of the man in the cab.

There are many workers at the roundhouse—machinists, boilermakers, helpers, wipers, and so on. A foreman is in charge. He receives reports from the locomotive engineers and inspectors on the condition of the engines and decides what work shall be done on them. At each engine terminal there is at least one hostler. The hostler is capable of running the engines. One of his jobs is to drive the engines in and out of the roundhouse. A hostler is about to take the engine in the picture out to the track where it will be placed in readiness for its next trip.