I found out the Walnut Hill Cemetery is in Marion County, Illinois, in the Village of Walnut Hill,Illinois. They do have a phone number but when I called no answer. It might be they are only there so many hours out of the week since it is very small. You could also call Marion County Courthouse in Salem, Illinois. The cemetery is on highway 37. I had the phone number for Walnut Hill City hall but can not find it now when I do will send it to you.
Lots of luck,