The wounding of Devil Dan Sickles and the stand of the 9th Massachusetts Battery. | American Battlefield Trust

In 1859, New York Congressman Daniel E. Sickles shot and killed Philip Barton Key II in broad daylight in Lafayette Square, Washington D.C., after discovering Key's affair with his wife Teresa. The murder shocked the nation – Key was the son of Francis Scott Key, author of "The Star Spangled Banner," and a prominent district attorney. Sickles surrendered immediately, telling reporters that he and Key "could no longer live on the same planet." The subsequent trial became a national sensation. Sic