This abandoned railway line began life in 1863 as the Richmond and Covington Railroad. Its terminus in Ohio was in Bradford at the junction with the Columbus to Chicago Main Line (also abandoned, see Columbus, OH to Ridgeville, IN). It eventually became part of the Pittsburgh, Cincinnati, Chicago and St. Louis Railroad, itself becoming officially part of the Pennsylvania Railroad in 1921. The PRR merged with the NYC in 1968 to become the Penn Central, subsequently becoming Conrail in 1976.
It is not entirely clear when the line was actually abandoned, however, since the Columbus to Chicago Main Line was abandoned circa 1983, it is probable the line was abandoned at the same time, if not earlier. Today, the interlocking tower still stands at Bradford, where the mainline splits; pictures can be found here.
Thanks to Aaron M. for contributing information about this route.