The day after my 73rd birthday, my husband, Rod, and I headed up the North Shore. We fled exhaustion and duties, immersing ourselves in glorious summer. Lake Superior operates like a cooling chamber, cold water mating with sunshine to put zip in the air, disperse biting bugs, and lay a light tan on your shoulders. Daily swims are possible both inland and, if you are brave enough, in Superior.

First stop, Tettegouche State Park.

If you hike the trail and wooden stairs down to where the Baptism River meets the lake, you find a perfect rock-rimmed swimming pool. Upstream, North Country waters...