A reproduction of John Stuart Mill's essay On Liberty (1859), formerly owned and heavily annotated by Joel Feinberg (1926-2004), is now available through the Princeton University Digital Library. Feinberg's copy of Mill's essay came into the possession of Michael Smith when he was a visiting professor at the University of Arizona at Tucson in 2001. Feinberg, a long-time faculty member at Arizona, and his wife, Betty, had decided to move into a smaller home, so he sold off most of his philosophy library to faculty and students for one dollar per book, the proceeds going to the department. Smith saw On Liberty for sale and, assuming it was the copy Feinberg referred to while writing his masterwork The Moral Limits of the Criminal Law, bought it for sentimental reasons without opening it. Feinberg had plainly read and re-read his copy of Mill's book many times, as it has been annotated using pencils, pens, and highlighters. Smith donated the book to the Princeton University Library in 2015. The reproduction is made available with the kind permission of Feinberg's literary executor, Betty Feinberg, and through the generous support of Princeton University and the hard work of the Philosophy and Religion Librarian Wayne Bivens-Tatum.