The classes MK-5 and MK-6 consisted of a total of 94 Mikados built for the Southern Pacific and its subsidiary Texas & New Orleans between 1913 and 1921. In contrast to earlier SP Mikados they were a Harriman standard design and had taller drivers and larger cylinders. 17 of the actual class MK-5 were built by Baldwin and Lima between 1913 and 1917. 20 more which were only built by Lima were designated class MK-6.

The T&NO got a total of 57 MK-5. Most were built by Baldwin, ALCO-Brooks and the SP Algiers shops, with only one delivered from the Houston shops. All of these had disappeared by 1957. Today four MK-5 are still existing, even though none is currently operational. While 771 will remain stationary, 745 and 786 ware being overhauled or restored, while there are plans to do the same with 794.