One of the reasons for the Cotter roundhouse was the lay of the land. From Batesville to Cotter, the route was built along the banks of the White River, and followed the slightly uphill course to the foothills of the Ozark Mountains at Cotter. So more power was needed to get the trains out of Cotter and up into the Ozark Mountains (really, just steep hills). The MP favored Consolidation locomotives (2-8-0), so for a period of time, westbound trains arriving in Cotter had their locomotives replaced with double-headed 2-8-0s. According to Walter (Mike) Adams book, 'The White River Railway', the assets of the White River Railway were conveyed to the St. Louis Iron Mountain & Southern, and later, the Missouri Pacific. The roundhouse was first planned under the White River Railway, constructed under the StLIM&S, and completed under MP ownership. Here are a few quotes from the book: 'The company did announce that the roundhouse at Crane would be identical to the one at Cotter and would be built from the same blueprints and by the same B&B forces, just as soon as they finished the work at Cotter. Like everything else on the division, the work on the roundhouse at Cotter suffered from the attentions of the old river. In early March, 1906 a rise threatened to inundate the new structure and less than a month later high winds blew down a portion of the roundhouse walls. Notwithstanding this, the work went on and in late April, 1906 certain B&B crews started moving out of Cotter for Crane. On July 4, 1906, the new turntable was placed in service at Cotter. This eliminated the temporary table installed when it became necessary to remove the wye track to make room for the roundhouse. The old table was far from satisfactory and the crews heartily welcomed the new one. The new table was a standard Philadelphia Bridge Works steel deck girder, 74 feet and 6 inches long. The table was hand operated and the pit was enclosed with a concrete wall and the floor was paved with brick. The concrete pedestal was poured on a footing of deeply driven pilings. An identical table was installed at Crane. The roundhouse was still not complete, being held up waiting for some vital machinery and tools, but when the turntable was completed, engines could be run in out of the weather and some servicing carried out. When a big engine showed up, say a Spot or 1 Class locomotive, everyone within shouting distance was rounded up to man the 'push sticks'. When the 1200's (2-8-2's) arrived on the north end of the division in 1927, after fighting their weight for two years, management finally approved an AFE (Authority For Expenditures) in October 1929 to install an air-operated tractor. Since the cost of this installation was only $1135.98, one wonders why it took so long to get the AFE approved. It sure cut down on the incidence of hernias among the work force at the Cotter roundhouse. In October 1950 the Division was dieselized, Engine #14 (2-8-0) left Cotter under steam on Train #269 headed for Newport and the Arkansas Division, and an era ended. The Cotter roundhouse was closed, no more would the flooding of the White River coat the floor with a foot of mud, no more would the 'big whistle' signal a train 'in the ditch'. The roundhouse, coal chutes, and water tanks were on a standby basis. Before the end of the year (1950), all machinery was dismantled and moved to Sedalia.

On the MoPac, a select few GP7's had a 'crew cab'. These units were originally on the Texas & Pacific and Gulf Coast Lines. Outwardly they looked like any regular Geep with the exception that the crew-cabs were modified with an extra set of number board cut-outs/windows that were exactly the same size as the number boards located just below the usual number boards on the short hood/nose. Behind the windows inside the cab sat a spare seat... right beside the typical toilet. The 'crew-cab' GP7s used by I-GN and STLB&M (series 4116-4123) were equipped with crew-cabs (modified circa 1953): 4117, 4119, 4120, 4122, and 4123. Since no other unit's received the crew cab, it's speculated that this modification may have been a 'Texas thing' for the brakeman to ride inside the unit.

The rebuilding process utilized a used EMD 12-567A normally aspired prime mover from a retired E-unit, replacing the unreliable Alco 12 cylinder Model 244G turbocharged prime mover. The North Little Rock Shops also installed a custom three-stack exhaust mainfold and replaced Alco's mechanically-driven radiator fan with EMD electrically-driven fans. Almost 600 horsepower was lost in the conversion, however this was not a concern to MP, since the RS3m/GP12 locomotives were to be assigned as yard power. This unit was retired in December 1974 and traded to GE.