Split Rock Lighthouse
First lit on July 31 of 1910 the Split Rock Lighthouse has been a beacon to mariners and tourists for over 100 years. The lighthouse itself is operated by the MN Historical Society, so your state park pass won't get you a tour. It's well worth the $9 admission ($7 for seniors, $6 for children 6-17), though.
Even if you don't take the official tour you'll find a wealth of natural beauty to explore between the pebble beach and the numerous trails.