[a] Mileage 1852 for January to September (no record of mileage recorded in Annual Reports previous to 1852).
[b] 15,000 to 20,000 miles per year was considered very high mileage for a locomotive of the 1850's.
[c] No mileage reported for any engines due to fire.
[e] The Pennsylvania Railroad claims a total mileage of 255,675. This may be accounted for by records of mileages for 1862, 1870, and 1879.
In 1871 the _Pioneer_ was remodeled by A. S. Hull, master mechanic of the railroad. The exact nature of the alterations cannot be determined, as no drawings or photographs of the engine previous to this time are known to exist. In fact, the drawing (fig. 8) prepared by Hull in 1876 to show the engine as remodeled in 1871 is the oldest known illustration of the _Pioneer_. Paul Westhaeffer, a lifelong student of Cumberland Valley R. R. history, states that according to an interview with one of Hull's descendants the only alteration made to the _Pioneer_ during the 1871 "remodeling" was the addition of a handbrake. The road's annual report of 1853 describes the _Pioneer_ as a six-wheel tank engine. The report of 1854 mentions that the _Pioneer_ used link motion. These statements are enough to give substance to the idea that the basic arrangement has survived unaltered and that it has not been extensively rebuilt, as was the _Jenny Lind_ in 1878.
By the 1870's, the _Pioneer_ was too light for the heavier cars then in use and by 1880 it had reached the end of its usefulness for regular service. After nearly thirty years on the road it had run 255,675 miles. Two new passenger locomotives were purchased in 1880 to handle the heavier trains. In 1881 the _Pioneer_ was dropped from the roster, but was used until about 1890 for work trains. After this time it was stored in a shed at Falling Spring, Pennsylvania, near the Chambersburg yards of the C.V.R.R.
[Illustration: Figure 11.--"PIONEER," ABOUT 1901, scene unknown. (_Photo courtesy of Thomas Norrell._)]
After the early 1840's the single-axle locomotive, having one pair of driving wheels, was largely superseded by the 8-wheel engine. The desire to operate longer trains and the need for engines of greater traction to overcome the steep grades of American roads called for coupled driving wheels and machines of greater weight than the 4--2--0. After the introduction of the 4--4--0, the single-axle engine received little attention in this country except for light service or such special tasks as inspection or dummy engines.