1804 was a leap year starting on Sunday (see link for calendar).

Events

• January 1 - End of French rule in Haiti
• February 14 - First Serbian Uprising began.
• 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 21 - The first self-propelling steam engine or steam locomotive makes its outing at the Pen-y-Darren ironworks in Wales. Designed by Richard Trevithick, a Cornishman.
• 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 20 - Execution of the Duc d’Enghien for plotting against Napoleon
• March 21 - Code Napoleon adopted as French civil law
• April 26 - Henry Addington resigns as Prime Minister of the United Kingdom
• May 10 - William Pitt the younger begins his second term as a Prime Minister of the United Kingdom
• May 14 - The Lewis and Clark Expedition departs from Camp Dubois and begin their historic journey by traveling up the Missouri River.
• May 18 - Napoleon Bonaparte is proclaimed Emperor of France by the French Senate.
• June 15 - The Twelfth Amendment to the U.S. Constitution ratified by New Hampshire, and arguably becomes effective (subsequently vetoed by the Governor of New Hampshire)
• 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 it first and last death when Sergeant Charles Floyd dies, apparently from acute appendicitis.
• September 1 - German astronomer K. L. Harding discovers the asteroid Juno
• Thomas Jefferson defeats Charles C. Pinckney in U.S. presidential election
• November 30 - The Jeffersonian 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 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 France in a thousand years (the Napoleonic Code is adopted).
• December 12 - Spain declares war on Britain

Unknown date

• Père Lachaise Cemetery a 118 acre (0.5 km²) cemetery in Paris, France is founded.
• Nicolas-François Appert (1750-1841) develops a method to preserve food by means of canning.

Ongoing events

• Napoleonic Wars (1799-1815)

Births

• January 1 - James Fannin, Texas revolutionary (d. 1836)
• January 20 - Eugène Sue, French novelist (d. 1857)
• January 21 - Eliza Roxcy Snow, American poet (d. 1887)
• February 7 - John Deere, American industrialist (d. 1886)
• March 14 - Johann Strauss Senior, Austrian composer (d. 1849)
• March 17 - Jim Bridger, American trapper and explorer (d. 1881)
• June 1 - Mikhail Glinka, Russian composer (d. 1857)
• June 24 - Willard Richards, American religious leader (d. 1854)
• July 1 - George Sand (Amantine Aurore Lucile Dupin), French writer (d. 1876)
• July 4 - Nathaniel Hawthorne, American writer (d. 1864)
• July 28 - Ludwig Feuerbach, German philosopher (d. 1872)
• September 8 - Eduard Mörike, German poet (d. 1875)
• September 27 - Anna McNeill Whistler, Whistler's mother (d. 1881)
• November 23 - Franklin Pierce, 14th president of the United States (d. 1869)
• December 21 - Benjamin Disraeli, British Prime Minister (d. 1881)

Deaths

• January 4 - Charlotte Ramsey Lennox, English author and poet (b. 1727)
• February 6 - Joseph Priestley, English chemist (b. 1733)
• February 12 - Immanuel Kant, German philosopher (b. 1724)
• March 21 - Louis-Antoine-Henri de Bourbon-Condé, duc d'Enghien (executed) (b. 1772)
• April 9 - Jacques Necker, French statesman (b. 1732)
• July 12 - Alexander Hamilton, American statesman
• September 4 - Richard Somers, American naval officer