June 30, 1520: Faced with an Aztec revolt against their rule, forces under the Spanish conquistador Hernán Cortés fight their way out of Tenochtitlan at heavy cost. Known to the Spanish as La Noche Triste, or “the Night of Sadness,” many soldiers drowned in Lake Texcoco when the vessel carrying them and Aztec treasures hoarded by Cortés sank. Montezuma II, the Aztec emperor who had become merely a subject of Cortés in the previous year, was also killed during the struggle; by the Aztecs or the Spanish, it is not known.

After sailing through the dangerous straits below South America that now bear his name, Portuguese navigator Ferdinand Magellan enters the Pacific Ocean with three ships, becoming the first European explorer to reach the Pacific from the Atlantic.