Union Pacific Big Boy (Paperback)

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Big Boy was the name given to the Union Pacific Railroad's twenty-five 4000 class 4-8-8-4 articulated steam locomotives built between 1941 and 1944 by Alco.The Union Pacific Railroad introduced the Challenger-type (4-6-6-4) locomotives in 1936 on its main line across Wyoming. For most of the distance the maximum grade is 0.82% in either direction, but the climb eastward from Ogden, Utah up the Wasatch grade (Wahsatch, on the railroad) is 1.14%, demanding a locomotive with greater tractive effort and horsepower to eliminate doubleheading and helper operations.