Class D7 on the Pennsylvania Railroad

Pennsylvania Railroad

The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....

 was a class of 4-4-0

4-4-0

Under the Whyte notation for the classification of steam locomotives, 4-4-0 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and no trailing wheels...

 steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

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Fifty-eight were built by the PRR's Altoona Works between 1882–1891 with 68 in (1.73 m) drivers, while sixty-one of class D7a were constructed with 62 in (1.57 m) drivers.

The D7 was fundamentally an anthracite-burning version of the PRR D6

PRR D6

Class D6 on the Pennsylvania Railroad was a class of 4-4-0 steam locomotive.Nineteen were built by the PRR's Altoona Works between 1881–1883...

, with a larger fire-grate in order to burn the slower-burning, harder coal.