World Population: Over 1 billion

Events of 1803

January–March

• January 5 – William Symington demonstrates his Charlotte Dundas, the "first practical steamboat".

January 5: steamboat Charlotte Dundas.

• January 30 – Monroe and Livingston sail for Paris to discuss, and possibly buy, New Orleans; they end completing the Louisiana Purchase.

• February 21 – Edward Despard and 6 others are hanged and beheaded for plotting to assassinate King George III and to destroy the Bank of England.

• February 24 – Marbury v. Madison: The Supreme Court of the United States establishes the principle of judicial review.

• February 25 – A major redistribution of territorial sovereignty within the Holy Roman Empire is enacted via an act known as the Reichsdeputationshauptschluss.

• March 1 – Ohio is admitted as the 17th U.S. state, retroactive from August 7, 1953.

• March 9 – Aargau becomes a Swiss canton.

• March 12 – Port Gibson, MS is chartered.

April–June

• April 30 – Louisiana Purchase is made by the United States from France.

• May – Napoleon I of France begins making preparations to invade England.

• May 18 – The United Kingdom resumes war on France after France refuses to withdraw from Dutch territory.

• May 19 – Master Malati, a Coptic Christian leader, is beheaded by a Muslim mob in Cairo, Egypt.

July–September

• 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 – The British begin the Second Anglo-Maratha War against Sindhia of Gwalior.

• September 3 – William Wordsworth wrote "Upon Westminster Bridge"

• September 20 – Irish rebel Robert Emmet is executed.

• September 23 – Battle of Assaye (India): British-led troops defeat Maratha forces.

October–December

• October 20 – The Senate ratifies the Louisiana Purchase Treaty, doubling the size of the United States.

• November 18- Battle of Vertières: The Haitian army led by Jean-Jacques Dessalines defeats the army of Napoleon.

• November 30 – At the Cabildo building in New Orleans, Spanish representatives Governor Manuel de Salcedo and the Marqués de Casa Calvo, officially transfer the Louisiana Territory to French representative Prefect Pierre Clément de Laussat (just 20 days later, France transfers the same land to the United States as the Louisiana Purchase).

Undated

• France – the Livre Tournois (Tours Pound) is replaced by the Franc.

• Graubünden, St. Gallen, Thurgau, the Ticino and Vaud become Swiss cantons.

• William Osgoode, Chief Justice of Lower Canada, rules that slavery is inconsistent with British law.

• Orissa, India is occupied by the British under the British East India Company after the Second Anglo-Maratha War.

• Major breakthroughs in chemistry occur, with the identification of the elements Rhodium, Palladium, Osmium, Iridium, and Cerium.

Ongoing events

• Napoleonic Wars (1799–1815).

Births

January–June

• February 2 – Albert Sidney Johnston, American Confederate general (d. 1862)

• February 15 – John Sutter, American pioneer (d. 1880)

• April 7 – Flora Tristan, French feminist (d. 1844)

• April 30

• *Jeremiah E. Cary, American politician (d. 1888)

• *Albrecht Graf von Roon, Prime Minister of Prussia (d. 1879)

• May 12 – Justus von Liebig, German chemist (d. 1873)

• May 24 – Charles Lucien Bonaparte, French naturalist and ornithologist (d. 1857)

• May 25

• *Edward George Bulwer-Lytton, English novelist and playwright (d. 1873)

• *Ralph Waldo Emerson, American writer (d. 1882)

• June 24 – George James Webb, English-born composer (d. 1887)

July–December

• July 10 – William Todd (1803-1873), American businessman, Canadian senate nominee

• July 24 – Adolphe Charles Adam, French composer (d. 1856)

• July 31 – John Ericsson, Swedish inventor and engineer (d. 1889)

• August 27 – Edward Beecher, American theologian (d. 1895)

• 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)

• September 29 – Mercator Cooper, American sea captain (d. 1872)

• November 14 – Jacob Abbott, American writer (d. 1879)

• November 29 – Christian Doppler, Austrian mathematician (d. 1853)

• December 6 – Susanna Moodie, English writer (d. 1885)

• December 11 – Hector Berlioz, French composer (d. 1869)

Deaths

January–June

• January 18 – Ippolit Bogdanovich, Russian poet (b. 1743)

• January 23 – Arthur Guinness, Irish brewer (b. 1725)

• February 9 – Jean François de Saint-Lambert, French poet (b. 1716)

• February 18 – Johann Wilhelm Ludwig Gleim, German poet (b. 1719)

• February 20 – Marie Dumesnil, French actress (b. 1713)

• February 21 – Edward Marcus Despard, British revolutionary (b. 1751)

• March 14 – Friedrich Gottlieb Klopstock, German poet (b. 1724)

• April 2 – Sir James Montgomery, 1st Baronet, Scottish politician and judge (b. 1721)

• April 7 – Toussaint L'Ouverture, Haitian revolutionary (b. 1743)

• June 24 – Matthew Thornton, American signer of the Declaration of Independence (b. 1714)

July–December

• August 24 – Napper Tandy, Irish republican

• September 5 – Pierre Choderlos de Laclos, French general and author (b. 1741)

• September 15 – Gian Francesco Albani, Italian Catholic cardinal (b. 1719)

• October 2 – Samuel Adams, American revolutionary leader (b. 1722)

• October 26 – Granville Leveson-Gower, 1st Marquess of Stafford, English politician (b. 1721)

• December 18 – Johann Gottfried Herder, German philosopher and writer (b. 1744)

• December 30 – Francis Lewis, American signer of the Declaration of Independence (b. 1713)

• Jacques-Donatien Le Ray, French Father of the American Revolution (b. 1726)