One really cool area before you hit Duluth is Jay Cooke State park. Definitely worth a stop and hike, lots of falls and rapids on that stretch of the St Louis River.
Kayak trips on Superior if weather allows are awesome. Also Sawbill is not far away if you want to try a day paddle in the BWCA.
Lots will recommend Gooseberry just due to proximity. But Tettegouchie and Cascade are far better hiking and have better falls along the way.
Grand Marais is the coolest town in the country. A great brewery and fish market all walkable from each other. Best fly shop in the Midwest if you are into that, have gotten to know him over the years and is always great to work with. Grand Marais is worth the long drive.
I could go on forever on the hidden gems that I’ve found on my many hiking and fishing trips up there but above are some of myself and kids favorites.