This railroad, known as the Columbus to Chicago Main Line, began life as the Columbus, Piqua and Indiana Railroad in 1858. After a series of acquisitions and mergers, it became the Pittsburgh, Cincinnati, Chicago and St. Louis Railroad in 1916. In 1921, the railroad became part of the Pennsylvania Railroad.
In its heyday, this line was one of the PRR's mainlines, and (based on system maps) was double tracked for the majority of the route. Between Urbana, OH and Piqua, OH, this line was triple-tracked. At Bradford, the Columbus-to-Indianapolis (via Bradford) main line branched out and went south (also abandoned, see Bradford, OH to Indianapolis, IN).
Tragedy struck on May 21, 1945, when a westbound train carrying soldiers home from the war derailed, killing 1 and injuring 24. Details of this wreck can be found here.
In 1968, the PRR merged with the NYC to become the Penn Central, itself becoming part of Conrail in 1976. Conrail abandoned this route in 1983.
Today, the ROW remains largely undeveloped, except in Piqua, OH, where an 11-mile long railtrail, dubbed "Linear Park" has been built.
Thanks to Aaron M. for contributing information about this route.