The first Mikados on the Milwaukee Road consisted of 20 saturated class L1 locomotives built by the company's own shops in Milwaukee in 1909. They already had a combustion chamber and drivers with a diameter of 63 inches. From 1912 onwards the L2 class followed, 40 of which were built in their own shops. Another 115 came from ALCO-Brooks and 25 from ALCO-Schenectady. Baldwin delivered 100 of the L2-a and L2-b classes from 1920 and 1922, respectively, which had a longer combustion chamber and, in the case of the L2-b, a larger superheater. The first ones were decommissioned in the 1930s after they were replaced by more powerful freight locomotives. Basically, a large proportion survived into the fifties, including ten L1s that were later given a superheater. 