The present collection of Contributions, Papers 34-44, comprises Bulletin 240. Each of these papers has been previously published in separate form. The year of publication is shown on the last page of each paper. FRANK A. TAYLOR _Director, United States National Museum_ CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY: PAPER 42 THE "PIONEER": LIGHT PASSENGER LOCOMOTIVE OF 1851 IN THE MUSEUM OF HISTORY AND TECHNOLOGY _John H. White_ THE CUMBERLAND VALLEY RAILROAD 244 SERVICE HISTORY OF THE "PIONEER" 249 MECHANICAL DESCRIPTION OF THE "PIONEER" 251 [FOOTNOTES] [INDEX] [Illustration: Figure 1.--THE "PIONEER," BUILT IN 1851, shown here as renovated and exhibited in the Museum of History and Technology, 1964. In 1960 the locomotive was given to the Smithsonian Institution by the Pennsylvania Railroad through John S. Fair, Jr. (Smithsonian photo 63344B.)] _John H. White_ The "PIONEER": LIGHT PASSENGER LOCOMOTIVE of 1851 _In the Museum of History and Technology_ _In the mid-nineteenth century there was a renewed interest in the light, single-axle locomotives which were proving so very successful for passenger traffic. These engines were built in limited number by nearly every well-known maker, and among the few remaining is the 6-wheel "Pioneer," on display in the Museum of History and Technology, Smithsonian Institution. This locomotive is a true representation of a light passenger locomotive of 1851 and a historic relic of the mid-nineteenth century._ THE AUTHOR: _John H. White is associate curator of transportation in the Smithsonian Institution's Museum of History and Technology._ The "PIONEER" is an unusual locomotive and on first inspection would seem to be imperfect for service on an American railroad of the 1850's. This locomotive has only one pair of driving wheels and no truck, an arrangement which marks it as very different from the highly successful standard 8-wheel engine of this period. All six wheels of the _Pioneer_ are rigidly attached to the frame. It is only half the size of an 8-wheel engine of 1851 and about the same size of the 4--2--0 so common in this country some 20 years earlier. Its general arrangement is that of the rigid English locomotive which had, years earlier, proven unsuitable for use on U.S. railroads. These objections are more apparent than real, for the _Pioneer_, and other engines of the same design, proved eminently successful when used in the service for which they were built, that of light passenger traffic. The _Pioneer's_ rigid wheelbase is no problem, for when it is compared to that of an 8-wheel engine it is found to be about four feet less; and its small size is no problem when we realize it was not intended for heavy service. Figure 2, a diagram, is a comparison of the _Pioneer_ and a standard 8-wheel locomotive.