The Cairo & St. Louis built a narrow gauge railroad from East St. Louis to Cairo through Murphysboro, IL. "When completed on February 19, 1875, at 146 miles it was the second largest in the country." It went bankrupt in 1877 when the Kaolin Tunnel collapsed. But after reorganization in 1881 as the St. Louis & Cairo, it proved a profitable hauler of coal from the Big Muddy coalfield near Murphysboro. [American Narrow Gauge Railroads and hit the previous button]
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]