In 1913 and 1914, the MKT received 60 Mikados from ALCO-Brooks with Walschaerts valve gear, which were listed as class L-1a. Their Number was augmented in 1914 by ten more, which received Baker valve gear and were listed as Class L-1b because of this difference. They were initially coal fired but underwent a conversion to oil firing by 1922. The new tenders now held 2,990 gallons of oil instead of 14 short tons of coal and had a slightly smaller water reserve. The boiler pressure had meanwhile been increased from 185 to 195 psi.