1803 was a common year starting on Saturday (see link for calendar).

Events

• January 30 - Monroe and Livingston sail for Paris to discuss, and possibly buy, New Orleans. They end completing the Louisiana Purchase.
• February 24 - The Supreme Court of the United States, in Marbury v. Madison, establishes the principle of judicial review.
• March 1 - Ohio is admitted as the 17th U.S. state, retroactive from August 7, 1953.
• April 30 - Louisiana Purchase made by the United States from France.
• May 18 - The United Kingdom redeclares war on France after France refused to withdraw from Dutch territory.
• July 4 - The Louisiana Purchase is announced to the American people.
• July 5 - The convention of Artlenburg leads to the French occupation of Hanover (which had been ruled by the British king).
• July 23 - Robert Emmet's uprising in Ireland begins
• July 26 - The wagonway between Wandsworth and Croydon is opened, being the first public railway line of the world.
• August 3 – British begin Second Anglo-Maratha War against Sindhia of Gwalior
• September 20 - Irish rebel Robert Emmet is executed
• September 23 - The Battle of Assaye in India – British-lead troops defeat Maratha forces
• October 20 - Senate ratifies the Louisiana Purchase Treaty, doubling the size of the United States.
• November 30 - At the Cabildo building in New Orleans, Spanish representatives Governor Manuel de Salcedo and the Marqués de Casa Calvo , officially transfer Louisiana Territory to French representative Prefect Pierre Clément de Laussat (just 20 days later, France had transferred the same land to the United States as the Louisiana Purchase).

• Aargau, Graubünden, St. Gallen, Thurgau, the Ticino, Vaud become Swiss cantons.
• France - the Livre Tournois (Tours Pound) is replaced by the Franc.
• William Osgoode , Chief Justice of Lower Canada, rules that slavery is inconsistent with British Law.

Ongoing events

• Napoleonic Wars (1799-1815)

Births

• February 2 - Albert Sidney Johnston, Confederate general (d. 1862)
• February 15 - John Sutter, California pioneer (d. 1880)
• April 7 - Flora Tristan, French feminist (d. 1844)
• May 12 - Justus von Liebig, German chemist (d. 1873)
• May 24 - Charles Lucien Bonaparte, French naturalist and ornithologist (d. 1857)
• May 25 - Ralph Waldo Emerson, American writer (d. 1882)
• May 25 - Edward George Bulwer-Lytton, English novelist and playwright (d. 1873)
• June 24 - George James Webb, English-born composer (d. 1887)
• July 24 - Adolphe Charles Adam, French composer (d. 1856)
• July 31 - John Ericsson, Swedish inventor and engineer (d. 1889)
• September 4 - Sarah Childress Polk, First Lady of the United States (d. 1891)
• September 27 - Samuel Francis du Pont, American admiral (d. 1865)
• September 28 - Prosper Mérimée, French writer (d. 1870)
• November 14 - Jacob Abbott, American writer (d. 1879)
• November 29 - Christian Doppler, Austrian mathematician (d. 1853)
• December 11 - Hector Berlioz, French composer (d. 1869)

Deaths

• March 14 - Friedrich Gottlieb Klopstock, German poet (b. 1724)
• April 7 - Toussaint L'Ouverture, Haitian revolutionary (b. 1743)
• September 5 - Pierre Choderlos de Laclos, French general and author (b. 1741)
• September 27 - Samuel Adams, American patriot (b. 1722)
• December 18 - Johann Gottfried Herder, German philosopher and writer (b. 1744)
• Jacques-Donatien Le Ray, French "Father of the American Revolution" (b. 1726)