Yellowstone Lake State Park Campground

 This is a very large state park located halfway between Mineral Point and New Glarus, both nice visiting destinations in their own right.
It has a large lake with three boat launches, a main one with a motor ramp, a canoe launch near the marshy end, and a fishing pier. There's also a boat rental place run by the nearby Cork Down Saloon. There are no boat-in or lake accessible campsites however.
 The campground is up a long 30 degree hill across from the main launch and Beach/ main picnic area. The sites are more secluded from each other than you'll find at most parks , which is very nice. Beware that some sites are so secluded that they are bi-level. That is, parking pad and then step(s) down to the site. Be sure to check the photos provided when reserving.  There are very nice walk-in sites, but no carts are provided.
the facilities are clean, but there's only one building with running water and showers. Water throughout has a mild iron taste.
There's no playground in the camp area, it's located in a picnic area near the canoe launch that you pass as you com in. Not walking distance, remember the big hill.
 There's an Ice Cream/concession at the east end of the lake with limited hours. Beyond that is the Cork Down Saloon, just outside the secondary entrance to the park. It's your closest option to eat out. Also there is the private Chalet campground (see others for a review) Neither has a view of the lake as they are below the Dam.
A fun place to visit in the area is the Toy Train Barn Museum in Argyle, indoors if you have a rainy day.

This campground offers sites with electricity for RVs but some of the sites seem pretty narrow to use RV awnings. We booked an RV site but decided to camp. The site had a picnic table and fire ring but since it was an RV spot not a lot of good tent placement options. There are numerous pit toilets to use. The park has hiking trails that are accessible from the campground. The lake has a walking trail, kayak ramps and boat ramps.

Very nice park. Well marked and maintained trails. A large lake with boat launch and beach area. Separate pet area.

We spent the weekend at site 101, which is a tent site. I wouldn't recommend this site. based on a quick walkaround, it seemed a bit smaller than other sites. That's not really a deal-breaker, but it didn't really have any flat spots to pitch the tent. We ended up pitching it up on the parking area, but it was still a bit slanted and we could feel the tire divot a little through the air mattresses. Aside from that, it was great. The site had a picnic table and fire ring that we used a lot. It was secluded from the surrounding sites.

We hiked the Windy Ridge trail and the Prairie Loop trail. both were well maintained and enjoyable trails. We also spent some time on the beach.