The St. Croix River, the free-flowing boundary between Wisconsin and Minnesota, is a federally protected National Scenic Riverway. The area’s first recorded human inhabitants were the Dakota Indians, whose lands were transformed by fur trade empires and the loggers who called it the “river of pine.” A patchwork of farms, cultivated by immigrants from many countries, followed the cutover forests. Today, the St. Croix River Valley is a tourist haven in the land of sky-blue waters and a peaceful escape for residents of the bustling Minneapolis–St. Paul metropolitan region. North Woods River is a thoughtful biography of the river over the course of more than three hundred years. Eileen McMahon and Theodore Karamanski track the river’s social and environmental transformation as newcomers changed the river basin and, in turn, were changed by it. The history of the St. Croix revealed here offers larger lessons about the future management of beautiful and fragile wild waters.