In 1851, the Cumberland Valley had a tank locomotive built by Seth Wilmarth, which was intended for passenger trains with a small number of passengers. The basic idea was to keep the ratio of the empty weight of the locomotive to the weight of the train as advantageous as possible in order to save costs. It had the wheel arrangement 2-2-2, which was generally very rare in tank locomotives and was hardly found in the USA, even with tender locomotives. In addition to the “Pioneer” there was also the almost identical “Jenny Lind” and two other very similar locomotives.

The “Pioneer” could accelerate a train of four passenger cars to 40 mph and achieved a high mileage for several years for its standards. After the Civil War, it was used to haul work trains because its power was no longer sufficient for modern passenger trains. Although it was later put into storage, it officially remained in service until 1901. It was then donated to the Smithsonian Institution and used as a working display at appropriate events.