The strange thing here is that you drive to an island. A causeway carries your car onto 28,000 acres of grassland where bison have run since twelve were brought over in 1893, and the herd now holds between 550 and 700 head. Plan around the gnats, which emerge April through June and shrug off insect repellent, so pack a fine mesh head net. Frary Peak tops out at 6,596 feet with almost no shade on the climb.
Do this: Hiking (Frary Peak), biking, bison viewing, stargazing, floating in the lake
Family note: Kids LOVE the bison and the beach
Fees and hours: stateparks.utah.gov
Add to the trip: Frary Peak (Hike, 3 mi) · Adams Canyon (Hike, 17 mi) · Ensign Peak (Hike, 20 mi) · Waterfall Canyon (Hike, 22 mi)