Does Union have a hilly or flat terrain
Back in 1998, I bought a topo map book of SC from a higher end office supply in Aiken. Its called "South Carolina Atlas and Gazetteer" and "Topo Maps of the Entire State, Back Roads, Outdoor Recreation", published by DeLORME. Its 15.5 inches tall by 11 inches wide.
I used it to look at the topography of the places I used to deer hunt back when I deer hunted. I guess you could try finding it in Rock Hill or Charlotte. Good luck!