The class 3800 and its subclass 3876 were the last 2-10-2 locomotives of the Santa Fe. After their predecessors had been created by adding a trailing axle to a 2-10-0, the 3800 was created by lengthening a 2-8-2, what allowed for a much larger firebox. The 75 members of the class 3800 were built by Baldwin between 1919 and 1923 and were operated at a boiler pressure of 200 psi. They carried the numbers from 3800 to 3875, with the exception of the number 3829 that was given to a 2-10-4.

Between 1924 and 1927, 65 locomotives followed which got the numbers between 3876 and 3940. Due to some changes in the boiler, they are usually viewed as a subclass. They were operated at 220 psi, while the earlier ones were upgraded to 210 psi. While 36 of the main class had been built as coal burners and only the rest as oil burners, all of the subclass had originally been built as oil burners. 23 of these were built with a trailing truck booster, while 15 others got larger tenders which can be found in the specs for the 3876 given below. Some were later rebuilt with thermic syphons. While most of the class 3800 and its subclass were still running in 1950, they were gone by 1956.