Thanks for the information. A link from the Union Co museum led to a 1908 atlas which provided plat maps for the area. This showed a cemetery on property owned by Calvin A. Smith (T11S, R3W, Sec25) that is probably the one I'm looking for. Not an exact location, but evidence of where to look.

John Jackson Smith was born around 1843 (estimated from the Federal census records) in Alto Pass (Ridge), Union Co, and died some time after 1882 and (I think) before 1900. The latter date is based on his disappearance from the census records starting in 1900. I believe he lived in Union Co his entire life, but I'm not 100% certain of that after the 1880 census.