Wikipedia:Selected anniversaries/October 21
- 1600 - Tokugawa Ieyasu established military supermacy over rival Japanese clans in the Battle of Sekigahara, which marked the beginning of the Tokugawa shogunate, the final shogunate to rule in Japan.
- 1805 - Napoleonic Wars: Admiral Lord Nelson led the British fleet to defeat a combined French and Spanish navy in the Battle of Trafalgar.
- 1824 - Joseph Aspdin, an English bricklayer, received the patent for Portland cement.
- 1854 - Florence Nightingale and a staff of 38 nurses were sent to the Crimean War.
- 1945 - Argentine military officer and politician Juan Domingo Perón married popular actress Evita.
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