For many years, I've been hoping to get time to comb Thoreau's massive journals for expressions of his political views. David Gross has done it for me, and done it in an extremely clear and thorough way, with excellent notes and references.
Of course, Thoreau's reputation as a pre-eminent American (and anarchist) political thinker depends on his great essay "Civil Disobedience." Here, we see many sources of that essay, and developments out of it. Here too, you see the connections that Thoreau himself made between his political positions - his advocacy of freedom, especially in opposition to slavery in every sense - and his naturalism, or indeed, his whole understanding a reality, truth, and humanity. And one sees, as well, the very essence of American individualism, formulated centrally by Emerson (more or less Thoreau's mentor and best friend), but expressed as profoundly by Thoreau as by anyone in history.
Thoreau is among the best political thinkers - and certainly among the best writers - in our language. David Gross has done us all a service in truly displaying the depth and clarity of this thought.