A question from a patron prompted me to take another look at the quotation, "dissent is the highest form of patriotism."  This is probably one of the most frequent quotation questions for us, but I haven't taken a fresh look at it for several years.  Google Books has revolutionized the way I search for TJ quotations (which usually turn out to be non-TJ quotations, more often than not), and in this case it helped us pinpoint earlier origins for this quotation.  The general gist is that we can now trace this quotation back to at least the Vietnam era, when it seems to have been used heavily.  The absolute earliest occurrence I can find is a 1961 Quaker publication, The Use of Force in International Affairs.  While interesting, I don't think this publication would have been circulated widely enough for it to be responsible for this phrase entering the general consciousness.  But being used by the Mayor of New York City and being published (repeatedly, from what I can tell) in the New York Times might well do the trick.  Read my updated Thomas Jefferson Encyclopedia entry.