• February 23 - The Philadelphia College of Apothecaries[?] founds the first pharmacy[?] college.
• March 25 - Greece declares its independence from the Ottoman Empire, beginning the Greek War of Independence.
• September 27 - Mexico gains its independence from Spain.
• Greece declares independence from the Ottoman Empire, starting the Greek War of Independence.
• August 10 - Missouri is admitted as the 24th U.S. state.
• In the first known obscenity case in the United States, a Massachusetts court outlawed the John Cleland novel, Fanny Hill . The publisher, Peter Holmes, was convicted for printing a "lewd and obscene" novel.

Arts, Sciences, Literature and Philosophy

• 1821 in literature:

Births

• January 8 - James Longstreet, Confederate General (+ 1904)
• February 3 - Elizabeth Blackwell, first female physician in the United States
• February 11 - Hermann Allmers[?], writer, and Auguste Edouard Mariette[?], French Egyptologist who dug out the Sphinx.
• February 17 - Eliza Rosanna Gilbert, better known as Lola Montez
• April 9 - Charles-Pierre Baudelaire, French poet and writer (+ 1867)
• May 8 - Jean Henri Dunant, founder of the Red Cross and recipient of the Nobel Prize in peace 1901 (+ 1910)
• May 17 - Sebastian Kneipp[?], naturopathist[?] (+ 1897)
• July 18 - Pauline Garcia-Viardot, composer
• August 10 - Jay Cooke, financier (+ 1905)
• October 13 - Rudolf Virchow, German doctor, pathologist, biologist, and politician
• October 30 - Fyodor Dostoevsky (+ 1881)

Deaths

• January 4 - Elizabeth Ann Seton[?], American saint
• February 23 - John Keats, British poet, dies in Rome
• May 5 - Napoleon
• May 19 - Camille Jordan, French politician