1220 Wamplers Lake Road, Onsted, MI 49265
Hayes State Park web page from the Michigan DNR.
We went this weekend and had a great time. It wasn't crowded (but I could see that it could get crowded during the MIS season) and the sites were all pretty nice. They have some fishing docks, and the kids got to go fishing, plus there's all the Irish Hills kitschy stuff like the Mystery Hill (and it's AMAZING FORCE OF GRAVITY) and mini golf etc. to visit. It is near MSU's Hidden Lake Gardens, which we didn't visit, but I'd like to do so sometime. We had lunch at Jerry's Pub on Wamplers Lake on the deck, and the food was good and the view was wonderful. It was a sunny warm day - perfect for an Oberon, which we had.