Three spots that we highly recommend would be 1- Cascade River Waterfalls 2- Temperance River 3-Tettegooche State Park
The Cascade River waterfall series is a deep cut gorge with sections of dramatic waterfall drops and cascades worthy of a stop for all ages and ability levels. The walk is a short .5 mile total as you leave the parking area and then traverse either side of the gorge on trails and boardwalk bridges that give you views of each falls from both sides of the river. The power and force of the intense water pouring through the gorge reminds me of watching water fall over Niagara and swirl away into oblivion. Imagining falling into the water and being swept away is still a freaky experience I can't help but have when seeing the shear force of the water.
Tettegouche State Park was a free entry and is a short .5 mile hike from the car to a beautiful Lake Superior pebbled beach and swimming hole along the peaceful river. The 90 degree day we passed through, he river was full of people swimming the sandbar where the river meets the big lake. A couple was saying vows on the shoreline for a unique wedding locale as we journeyed past in route to the waterfall hike. 3/4 of a mile later we were treated to the rumbling sounds and of the waterfall and were able to get up close and personal on the rocks alongside the falls. This was a great little stretch of our legs on our way up the North Shore without detouring us too long from our final destination- the Boundary Waters.
The Temperance River is also right off of Highway 61 and offers beautiful sights of the river and unique bridge that passes over. Even from the highway you can see people enjoying the view.
The famous Split Rock Lighthouse can be seen from a pull off along Highway 61, where it sits as a stoic sentinel looking watch over the rough shores of Two Harbors. The Historical Society owns the grounds for the lighthouse however, so even to catch a closer glimpse of it, travelers must pay a hefty $12 per person admission. I suppose if this was a final destination for you it might be worth the price, but it is kind of a shame that it is so controlled that you simply can't get near it unless your family is willing to put down some serious cash.
There are numerous local eating options as well as you pop in and out of small towns like Two Harbors and Tofte. We enjoyed Hippie Tacos in Grand Marais and ice cream on the lighthouse wave breaks. People were out all over walking the walls and swimming off the lighthouse or gimping off the rocks into chilly Lake Superior. Our Rock Hopper took a brave dip as well, a right of passage for any young boy.
Each of these offer about an hour of exploration as a quick stop. Plan an extra 1/2 day at least along the way to account for all these great spots and opportunities to stretch your legs.