Baldwin built fifty of the 3400 class 4-6-2s between 1919 and 1924. They were the last pacifics bought by the Santa Fe, as the thirty-five "3500 class" 4-6-2s were balanced compounds, dating to 1914. The 3400s were designed by John Purcell, who became the ATSF's head of motive power in 1912. Purcell stopped the wild experimentation that marked the ATSF in the early years of the 20th century, when the ATSF bought balanced compounds and even more exotic articulateds with hinged boilers.

Under Purcell, the Santa Fe bought large groups of big locomotives, like the 2-8-2, 2-10-2 and 4-6-2. There was nothing fancy about these locomotives. They were simple two cylinder machines, that operated on slightly lower than normal boiler pressure and lacked most of the modern appliances that improved the efficiency of steam locomotives. Purcell felt the extra efficiencies were not worth the extra maintenance costs, and the AT&SF let other railroads do the innovating after 1912.

The 3400 class originally was equipped with 73" drivers, but between 1935 and 1941, the Topeka shops rebuilt all fifty into much better machines. Elesco feedwater heaters and 79" box-pok drivers were fitted, and the 3400s lasted until 1950, when they began to be retired. They were all gone by 1955, except the ones that were saved for display.