1804 (MDCCCIV, in Roman numerals) was a leap year of the 19th century of the current Gregorian Calendar, of the Age of Christ, and its dominical letters were A and G (52 weeks), it started on a Sunday and ended on a Monday. fair.
January 1 - From the city of Gonaïves, Dessalines officially declared Haiti's independence, ending French rule in the country. Haiti becomes the first black republic and the second independent country on the American continent after the United States.
25 April - King D. João VI of Portugal confirms the establishment of the Royal Order of the Noble Damas de Santa Isabel, an honorific and feminine order, whose grand master was his wife D. Carlota Joaquina.
May 28 - Napoleon Bonaparte is proclaimed Emperor of France.
August 11 - King Franz I of Austria founds the Austrian Empire, as a reaction to the creation of the 1st French Empire.
September 1 - Asteroid 3, Juno, discovered by Karl Harding.
December 12 - Spain declares war on England
Appointment of D. José António de Melo da Silva César de Meneses, Count of São Lourenço, in the position of Captain General of the Azores.
In Japan, Shimizu Kensetsu, one of the top five construction companies, is founded by Shimizu Kisuke.
Richard Trevithick built the world's first steam locomotive.
January - June
February 12 – Heinrich Lenz, German physicist (d. 1865).
April 5 – Matthias Schleiden, German botanist, co-founder of cell theory (d. 1881).
June 13 - Manoel Marques de Souza III, Count of Porto Alegre, Brazilian military (d. 1875).
June 24 - Stephan Ladislaus Endlicher, Austrian botanist and linguist (d. 1849).
June 28 - Franz Julius Ferdinand Meyen, German physician, botanist and zoologist (d. 1840).
July - December
July 1 – George Sand, French writer (d. 1876)
July 20 – Richard Owen, British biologist (d. 1892).
July 28 – Ludwig Feuerbach, philosopher (d. 1872).
September 14 - John Gould, English ornithologist and naturalist (d. 1881).
October 3 - Allan Kardec (codifier of the spiritist doctrine) (d. 1869).
October 18 - Mongkut, King of Siam (d. 1868).
October 24 – Wilhelm Eduard Weber, German physicist. (d. 1891).
November 6 - Nuno José Severo de Mendonça Rolim de Moura Barreto, Portuguese politician (d. 1875).
November 18 – Alfonso Ferrero la Marmora, Italian politician (d. 1878).
November 23 – Franklin Pierce, 14th President of the United States (d. 1869).
December 8 - António Moniz Barreto Corte Real, Portuguese politician, journalist, writer and high school teacher (d. 1888).
December 10 – Carl Gustav Jakob Jacobi, German scientist (d. 1851).
December 21 – Benjamin Disraeli, British writer and politician (d. 1881).
February 12 – Immanuel Kant, Prussian philosopher, generally regarded as the last great early philosopher of the modern era.
October 2 - Nicolas-Joseph Cugnot, French inventor who built what may have been the world's first self-propelled vehicle.
July 12 – Alexander Hamilton, Former United States Secretary of the Treasury. He was assassinated by the 3rd Vice President of the United States Aaron Burr in a duel.