Why did Alexander Hamilton and Aaron Burr duel?

Burr, a Republican, and Hamilton, a Federalist, had been bitter political rivals for years, beginning when Burr took Hamilton's father-in-law's seat in Congress.

In the 1800 Presidential election, Aaron Burr and Thomas Jefferson each received the same number of votes, enough to unseat the incumbent John Adams, but resulting in a tie for the presidency. The Electoral College was unable to resolve the tie, so the House of Representatives became responsible for determining the outcome of the race. Whichever man received the most House votes would become the next President; the other would be Vice-President.

The House attempted to resolve the stalemate in 36 votes over seven days. Alexander Hamilton, who was then Secretary of the Treasury, used his political influence to convince the Representatives to vote for Jefferson. Burr learned of Hamilton's political maneuver, which escalated the animosity between the two.

In 1804, after Burr had been defeated in the New York Gubernatorial race, he learned Hamilton had allegedly made some disparaging remarks about Burr's character. The particulars are unknown because Hamilton's insults were only implied, not quoted.

A man named Dr. Cooper wrote a private letter to an acquaintance, and the letter was somehow leaked to a newspaper. The part Burr found offensive:

"Genl. Hamilton and Judge Kent have declared in substance that they looked upon Mr. Burr to be a dangerous man, and one who ought not to be trusted with the reins of Government. I could detail to you a still more despicable opinion which General Hamilton has expressed of Mr. Burr."

Burr exchanged several letters with Alexander Hamilton requesting an apology, but Hamilton refused. Burr's initial approach seems to have been relatively straightforward and non-confrontational, but Hamilton's response was taunting and Burr's anger eventually escalated to the point of challenging Hamilton to a duel to defend his honor.

Hamilton accepted, but history tells us he intentionally fired into a tree limb about fourteen feet above and four feet wide of Burr's head. Burr either believed Hamilton intended to shoot him or simply took advantage of an opportunity (the truth has never been determined), and fired directly at Hamilton, hitting him in the abdomen. Hamilton sustained organ damage and a severed spinal cord, and died the next day, July 12, 1804.

Burr was charged with murder in both New York and New Jersey, where the duel was held, but the case was never prosecuted.

Additionally, some historians cite evidence that Hamilton decided in advance of the duel that he would not fire his weapon. Hamilton was wounded in his liver by Burr and died 33 hours later in New York. Before his death he reportedly forgave Burr.