"Bradford"
Bradford began, in 1852, as a construction camp of the Columbus, Piqua, and Indiana Railroad. When the Richmond and Covington Railroad made a junction here in 1864, the village grew with the railroad yard. There were 60 miles of track, a 50-stall roundhouse, and jobs for 2000 men. Community life in Bradford centered at the Railroad YMCA.
This is listed, and numbered as being in Darke County, though it appears it is just in Miami County. From what I can tell the county line runs north-south down OH-721. The marker stands on the East side of the road, so actually in Miami County. Maybe it stood elsewhere when it was originally placed.