1801 1802 1803 - 1804 - 1805 1806 1807
1770s 1780s 1790s - 1800s - 1810s 1820s 1830s
Events of 1804
- January 1 – Haiti becomes independent from France in a slave revolt commits genocide of all people of the European race on the island.
- February 14 – The First Serbian Uprising begins as an intro into Serbian revolution. By 1817, Principality of Serbia proclaims self-rule from Ottoman Empire, thus becoming the first nation-state in Central Europe.
- February 15 – New Jersey becomes the last northern state to abolish slavery.
- February 16 – First Barbary War: Stephen Decatur leads a raid to burn the pirate-held frigate Philadelphia.
- February 18 – Ohio University is chartered by the Ohio General Assembly.
- February 21 – The Cornishman Richard Trevithick's newly-built Penydarren steam locomotive operates on the Merthyr Tramroad between Penydarren in Merthyr Tydfil and Abercynon in South Wales, following several trials since February 13, the world's first locomotive to work on rails.
- March 7 – John Wedgwood founds The Royal Horticultural Society.
- March 10 – Louisiana Purchase: In St. Louis, a formal ceremony is conducted to transfer ownership of Louisiana Territory from France to the United States.
- March 21 – The Code Napoleon is adopted as French civil law.
- April 2 – Forty merchantmen are wrecked when a convoy led by the HMS Apollo runs aground off Portugal.
- April 5 – The first recorded meteorite falls in Possil, Scotland (High Possil Meteorite).
- April 26 – Henry Addington resigns as Prime Minister of the United Kingdom.
- May 10 – William Pitt the Younger begins his second term as Prime Minister of the United Kingdom.
- May 14 – The Lewis and Clark Expedition departs from Camp Dubois and begins their historic journey by traveling up the Missouri River.
- May 18 – Napoleon Bonaparte is proclaimed Emperor of the French by the French Senate.
- June 15 – The Twelfth Amendment to the U.S. Constitution is ratified by New Hampshire, and arguably becomes effective (subsequently vetoed by the Governor of New Hampshire).
- July 11 – Alexander Hamilton is shot during a duel with Aaron Burr and dies the next day.
- July 27 – The Twelfth Amendment to the U.S. Constitution ratified by Tennessee, removing doubt surrounding adoption.
- August 20 – Lewis and Clark Expedition: The Corps of Discovery, whose purpose is to explore the Louisiana Purchase, suffers its only death when Sergeant Charles Floyd dies, apparently from acute appendicitis.
- September 1 – German astronomer K. L. Harding discovers the asteroid Juno.
- November 20 – Said bin Sultan, Sultan of Muscat and Oman starts to rule.
- November 30 – The Democratic-Republican-controlled United States Senate begin an impeachment trial against Federalist-partisan Supreme Court of the United States Justice Samuel Chase (he was charged with political bias but was acquitted by the United States Senate of all charges on March 1, 1805).
- December 2 – At Notre Dame Cathedral in Paris, Napoleon Bonaparte crowns himself as the first Emperor of the French in a thousand years (the Napoleonic Code is adopted).
- December 3 – Thomas Jefferson defeats Charles C. Pinckney in the U.S. presidential election.
- December 12 – Spain declares war on Britain.
- Rattenbury, Gordon; Lewis, M. J. T. (2004). Merthyr Tydfil Tramroads and their Locomotives. Oxford: Railway & Canal Historical Society. ISBN 0-901461-52-0.