Hartman Creek State Park is one of our new favorite parks! This was our first camping trip here and we're very happy with it. Lots of water activities, including swimming, kayaking, canoeing, Maui mats, paddleboards, etc. Many items are available for rent at the beach concession stand (operated by Adventure Outfitters, LLC), as well as treats and basics.
We hiked about 6 miles, both on the Ice Age trail, and other connections on the return hike. Some of our group also did the easy and medium mountain bike trails. The only only complaint was that it was difficult to get off of the medium before an hour of riding; no connections. There are so many miles of both hiking and bike/hiking trails available here! I'm looking forward to returning again to explore more.
The lakes are just gorgeous. Marl Lake's deep blue color has to be seen to be believed.
Overall, I'd say it's in my top 5 Wisconsin State Parks, along with Devil's Lake, Harrington Beach, Wyalousing, and Governor Dodge.