On August 31, 1846, twenty-nine-year-old Henry David Thoreau left his cabin on Walden Pond to undertake a railroad and steamboat journey to Bangor, Maine, from where he would venture with his Penobscot guide Joe Polis deep into the backwoods of Maine. This account of his expedition, some think, is a profounder exploration of the philosophical themes of the more famous "Walden" than is the latter book, at least revealing his fundamental perspectives in embryonic form. Of particular interest is his sympathetic and penetrating observation of the Indian nations of Maine, especially the Penobscot and Passamaquoddy.