He apparently began a newspaper, which ran for many years. He also was an elected official for many years as County Clerk and recorder. And he died in 1908, while his widow died in 1917. If his local newspaper obit doesn't exist, maybe a nearby county newspaper would have it; or perhaps the State Archives of WV (on microfilm). If that fails, write to the current county clerk and see if they have a "memorial book" of some kind in their office for past elected officials.
Finally (if all else fails!) ask if they would look at the deed books for 1865-66 (or so) to see if J. Frank Johnson ever filed his military discharge paper in one of these. The county I live in (in Illinois) has a lot of "Misc." records recorded in the early deed books, including some discharge papers.
I don't know how early/late that they have death records, but you might want to check on that also. If not for him, then perhaps for Marinda, who died later.
Or search for a G.A.R. post(or SUV)near that area--they might hold some records.
I also read on the website that they Historical Society (a link)is selling a County History book for $60 (more importantly, Volume II---which means there is a Vol. I out there somewhere!). Most Society's don't mind looking up a person for you if they think they may sell a book in the process. You could probably get Vol. I through a local library (depending on where you live) via library loan system.
Why not click on that site (e-mail address is listed) and have them see if anyone submitted any information on J. Frank (Sr.) or Marinda?
Also, the WV GenWeb site has a "photograph" link. At the bottom of the picture link is an Historical Photograph book for sale (again an e-mail address) of McDowell County places & people.
Hope you find something!!
Ann