In Michigan's Upper Peninsula you'll find plenty of rock hunting, especially agates. We camped at Woodland Park in Grand Marais, MI and the beach had all the rocks you'd ever want. Plus the campground was on a short bluff right above the beach. It's water & electric only and they don't take reservations, but we were there in mid-July and had no problem with a campsite. Weekends can be a different matter though.
You can get to the campground website through RV Park Reviews.com.
http://www.rvparkreviews.com/regions/michigan/grand-maraisInfo on Grand Marais.
http://www.grandmaraismichigan.com/beaches-and-swimming.phpInfo on Lake Superior Agate Festival.
http://www.superiortrails.com/rock-agate-festival.htmlInfo on other agate beaches in the U.P.
http://www.superiortrails.com/agate-beaches-upper-peninsula.htmlNow, that's a lot of info on places to hunt for agates and more. The U.P. is a wonderful place to visit, especially along the Lake Superior shoreline. Pictured Rocks National Lakeshore isn't far west of Grand Marais in Munising. There's plenty of campgrounds throughout the U.P. The black flies can be bothersome, especially in the early summer. Even in the height of summer tourist season you'll find plenty of campsites available. Enjoy!
2018 Chevy 2500HD Duramax - 2015 Cedar Creek Silverback 29RE
16K Huskey EZ Roller Hitch - EU2000i Honda Generator