I found the telephone number for the Village of Walnut Hill in Marion County, Illinois. It is 618-532-2113.
I also found the names of the ones buried at the Old Walnut Hill Cemetery.There are only 13 names and four not readable sandstone.
Old Walnut Hill Cemetery
Section 26, Centralia Township, Marion County, Illinois
Hensley, Julia D.
Copple, Inf son
Thats it, hope its what you were looking for, and that I was of some help.