While a member of the state legislature in 1842, Abraham Lincoln butted heads with state Auditor James Shields. Shields, who eventually became the only politician to serve as a senator in 3 separate states, was criticized by Lincoln for his method of collecting taxes. To show his contempt for the man, Lincoln started a series of letters to the Sangamon Journal from the point of view of a widow called the "Lost Townships." The letters made satirical allusions to Shields and made fun of his tactics. Making things worse, Mary Todd Lincoln and a friend named Julia Jayne joined in, writing scathing personal letters to Shields calling him a fool and a liar.
When Shields learned Lincoln was complicit in writing the letters, he challenged Lincoln to a duel. According to tradition, the person challenged is the one who chooses both the location and the weapons used in a duel. Lincoln considered it ludicrous, but chose an open site on the western side of the river from Alton on Sunflower Island (later called Smallpox Island). Lincoln's weapons of choice were cavalry broadswords "of the largest size."
On September, 22, 1842 Shields arrived to face Lincoln and found him hacking away at an unfortunate willow tree. Seeing the long-armed reach of Lincoln and the ferocity with which he hammered at the tree, Shields quickly changed his mind about the duel and decided to settle the disagreement in a more civil manner.
The historic site marker for the Lincoln - Shields duel is on the Riverwalk across from the Alton Amphitheater overlooking the river.