Volume 37 covers the Union Pacific Challengers in the following groups: UP #3975-3999 (1943 series), and #3700-3717 (oil fuel). This will be an on going series of about 40 books covering all classes of Steam Locomotives of the UPRR and its subsidiaries. Each book is 80 pp., 11 x 8.5 horizontal format, printed on 100 lb. enamel stock and a soft cover. Each volume contains 77 quality photographs. Supporting technical data is included for the time the photo was taken. The books show a wide variety of photographic views that show locomotives during various eras, the various lettering and paint schemes, changes in appearance, with various tenders, as well as both sides of locomotives. The books contain photographs from noted photographers G.M. Best, R.H. Kindig, Don Roberts, R.J. Foster, Francis Gschwind, John Conant, Stan Kistler, W.O. Gibson, Art Peterson, Art Stensvad, Lou Schmitz, Jim Ehernberger, Dave Martindell, and others. Union Pacific Historical Society, soft cover, 80 pages, standard landscape book 10 x 8 in., Black-and-White photographs with captions.