I've just finished a book: 3012. Wheelan, Joseph. Mr. Adams’s Last Crusade, John Quincy Adams’s Extraordinary Post-Presidential Life in Congress. New York: Public Affairs, 2008. (P) It deals with his career in Congress after leaving the Presidency. JQA is one of the most admirable figures in our history. He did not accomplish much as President, but, in Congress, he became a towering figure and the conscience of the United States. In the movie Amistad, Hopkins played Adams so well it's uncanny. Adams's speech before the Supreme Court is available on the web. In real life, he delivered it in two sections of over 4 hours each, speaking without notes. Buy the book. It's worth it.
JQ Adams was possibly the best educated of all our presidents. He was amazingly successful as a diplomat, a great Secy of State, a leader in Congress in his later years. but, historians sometimes give him short shrift in his one term as POTUS. perhaps it was because JQ Adams tried to do too much too quickly as a National Republican.
