It was in a position to connect two other narrow gauge railroads --- Toledo, Cincinnati & St. Louis (TC&StL) to the northeast and Texas & St. Louis to the southwest to form the Grand Narrow Gauge Trunk. See American Narrow Gauge Railroads for a map. This trunk line effectively was the route that I-69 is supposed to be built to serve --- Houston/Mexico to Detroit/Toledo. Judging from the map, at least part of the TC&StL must have become part of the Cloverleaf, which became part of the Nickel Plate.
"In 1886 the M&O acquired the narrow-gauge St. Louis and Cairo Railroad and changed it to standard gauge, thus making possible a through haul from Mobile to St. Louis (except for the ferry service at Cairo)." [acmeme written by James H. Lemly]