St James, Sag Bridge (also known as "St James, The Sag", or just "St. James", or by us locals, as kids, as "Monks Castle") is the oldest Catholic cemetery in the Chicago Archdiocese. It was dedicated in 1837.
To me that is cool enough, but on top of all this is the legend surrounding this place: There are various stories of spooky sightings and general weirdness here, including reports of the ground "breathing" on the cemetery grounds.
There is some information here about the cemetery, but a bit of further online research shall definitely make your visit more interesting.
This cemetery can only be accessed from Route 171/Archer, and of course is open only during the hours one would expect a cemetery to be open. Bear in mind, when you visit, that there is an active church here, which is very popular for weddings and such, and that regular services are held here, so conduct yourselves accordingly (sorry if I sound condescending, but you never know).
Archer Avenue itself has a history of weirdness, including--to the northeast of this site, on Archer--the Willowbrook Ballroom, and still farther northeast, Resurrection Cemetery--both related, some would say, to the legend of "Resurrection Mary" the "hitchhiking ghost".
The cache itself is located as out of the way and unobtrusively as possible, and should certainly violate nobody's sense of decency or propriety. You should be able to see it, retrieve it, and do what you will with it without treading on anyone's grave or attracting attention. The cemetery is regularly visited by tourists, so do not hesitate to park in the lot there.
Interestingly, this cemetery also contains what is claimed to be the largest slippery elm tree in the state of Illinois. The tree is next to the church, and there is a comemmorative plaque on the path leading to the church entrance. I have posted photos of both tree and plaque in the gallery. They can be viewed at the links below.