Played Bent Creek in Lititz, Pennsylvania, this weekend. There's a very old family cemetery behind No. 13; I assume it was a farmer's family, as there's an old barn and farmhouse nearby. From what I could read on the gravestones, it looked like they were dated in the late 1700s, but I didn't enter the fenced in area to have a closer look.
I also played Heritage in Pawleys Island, South Carolina, this winter and they have a slave burial ground on No. 8. It's fenced off with a historical placard, but I fear that due to the hole's tee and green in relation to the cemetery, it may see some play, which is incredibly unfortunate.
Additionally, we played Bala in Philadelphia last fall and stumbled upon a very old cemetery in the trees behind No. 3. It was in very bad shape and I'm confident very few people know it exist. I couldn't make out any names, but I believe some of the years were in the mid-1700s. Not sure what kind of cemetery it is.