Along the Minnesota-Ontario border, in the days of voyageurs, tall trees were used as guideposts in the uncharted wilderness to help fur traders and explorers find their way through the maze of lakes and portages. Branches were cut, leaving the middle of the trees bare with branches above and below. Clifford and Isabel Ahlgren, two of the most knowledgeable ecologists of the area, use nine native trees to serve as lob trees for this book, an ecological history of human activity in the Quetico-Superior wilderness area.