According to the 1880 U.S. census, there is one Harry STRONG that was born ca 1873. This family lived in Loudonville, Ashland, OH: head, Henry, 40, OH, cabinet maker PA MD wife, Elizebeth, 39, OH, keeps house, PA PA dau, Florance, 20, OH dau, Eva, 18, OH dau, Iona, 16, OH dau, May, 13, IN son, Otto, 11, OH son, Harry, 6, OH dau, Ida, 3, OH
You would need to locate Henry's birth or death record and/or Henry and Elizabeth's marriage record, assuming that his father's name is on those documents.
A Henry STRONG md Mary E. (Elizabeth?) DOTY, on 19 May 1859 in Ashland Co. OH. You could try the Ashland Co. Probate Court; OH marriages were first recorded in 1835. That address is: Ashland County Courthouse 142 W. Second Street Ashland, Ohio 44805 Tel: 419-289-0000