Burr was born in Newark, New Jersey, to the Reverend Aaron Burr and Esther Edwards Burr. His maternal grandfather was the theologian Jonathan Edwards, and his paternal grandfather was one of the founders of the College of New Jersey, later Princeton. He originally studied theology, but changed to law after graduating from Princeton. His studies were put on hold for the Revolutionary War, in which he served under Benedict Arnold, George Washington and Israel Putnam. He was promoted to lieutenant colonel and commanded a regiment in the Battle of Monmouth, before resigning in 1779 due to poor health. In 1782, he passed his bar exam in New York.
Burr's main rival for dominance of the New York bar was Alexander Hamilton. Burr became involved in politics in 1789, when George Clinton appointed him Attorney General of New York. In 1791, he defeated a favored candidate for a seat in the United States Senate. He was not reelected and instead went into the New York legislature. Burr quickly became a key player in New York politics, more powerful than Hamilton, largely because of the Tammany Society, later to become the infamous Tammany Hall, which Burr converted from a social club into a political machine.
Because of his control of the crucial New York legislature, Burr was Jefferson's running-mate in the 1800 election. The state legislatures elected the electors to the U.S. Electoral College at that time, and New York would be a needed win for Jefferson. Jefferson did win New York and the election, but so did Burr; they both tied with 73 electoral votes. The election devolved to the House of Representatives, where it took three days and 36 ballots for the moderate Federalists supporting Burr to finally accept that he could not win. Burr's refusal to give the victory to Jefferson as he had promised cost him the trust of his own party and of Jefferson: for the rest of the administration, Burr was an outsider.
Burr did not run with Jefferson in the 1804 election. Instead he ran for the governorship of New York. Alexander Hamilton, his old rival, made insulting comments about him, and Burr responded with a challenge to a duel. On July 11, 1804, Aaron Burr shot and fatally wounded Hamilton in their duel in Weehawken, New Jersey. The bullet entered Hamilton below the chest. Wanted as a criminal in both New York and New Jersey, Burr fled to Philadelphia. There he met Jonathan Dayton.
Burr and Dayton together created a conspiracy, the goal of which is fairly vague. At its grandest, the plan was for Burr to make a massive new nation in the west, forged from conquered provinces of Mexico and the states west of the Appalachian Mountains. The plan was working nicely, until General James Wilkinson, a conspirator, betrayed Burr's plans to the president, who issued a proclamation for Burr's arrest. Burr read this in a newspaper in the Orleans Territory on January 10, 1807. He turned himself in to the authorities, but soon jumped bail and fled for Spanish Florida; he was intercepted in Alabama on February 19.
Four times in Richmond, Virginia, Burr was arraigned for treason before a grand jury. The fourth time, May 22, sufficient evidence was found to indict him. His trial, which was run by Chief Justice John Marshall, began August 3.
Due to lack of the constitutionally required two witnesses, Burr was acquitted on September 1. Burr was at this point without a hope of a comeback in politics, and fled America and his creditors for Europe, where he tried to regain his fortunes. He returned quietly to New York in 1812, and lived there as a moderately successful attorney until his death in 1836.
Another member of the Burr conspiracy was the Anglo-Irish Aristocrat Harman Blennerhassett. After marrying his niece, Blennerhasset had been forced out of Ireland. He came to live as a quasi-feudal lord on an island in the Ohio River. It was there that he met Burr and agreed to help finance the imperial ambitions of Burr's group.