Built in 1925 for the St. Louis-San Francisco Railway, #1526 was one of ten Mountain type (4-8-2) locomotives delivered to the railroad (#1520-#1529) designated Class T-54. Twenty of the class had been delivered in 1923
(#1500-#1519), and all thirty were built by
the Baldwin Locomotive Works in Philadelphia, PA.
Problems with the Baker gear on the earlier T54s, led the Frisco to order the next ten with Walschaert valve gear. They also featured other changes from the earlier T-54s. The firebox was fitted with thermic syphons contributing 84 sq ft of heating surface and an 89 sq ft combustion chamber.