Gay City State Park is an excellent trail running route. The red trail ends up being about 6 miles long but it allows a lot of “bailout” trails. My personal favorite is in the summer running about 3 miles in and cutting down one of the white trails to jump in the lake and jumping back on the trail and finishing up my last 3 miles on the red trail. At the end of my run, I would walk back down the road to the swimming lake and hang out for a bit to cool down. All the trails in the park are really well marked and easy to navigate.
This park gets extremely crowded in the summer because of the beach area. I do recommend Gay City State Park to all dog hikers as the trail is easy to navigate, there isn’t much elevation gain, and it’s a scenic area. Bonus is dogs can also go swimming in the non-designated swim spots which allows a nice cool down for them.
*Pups aren’t allowed to go swimming in the designated swim spot or the sand area in season.
*Lastly, they do charge to park in season.