Template:On this day - September 20

Francisco Valles de Covarrubias

• 1519 – The Magellan–Elcano expedition sets sail from Sanlúcar de Barrameda; it would achieve, for the first time in history, the circumnavigation of the planet.
• 1592 – Death of Francisco Valles de Covarrubias, Spanish physician considered the creator of modern anatomical pathology (b. 1524).
• 1596 – In the New Kingdom of León (present-day Mexico), Diego de Montemayor founds the city of Monterrey.
• 1604 – The Siege of Ostend ends with the victory of the Spanish tercios over the forces of the United Provinces.
• 1629 – A heavy rain, called the "Flood of Saint Matthew", which lasted 40 hours, leaves Mexico City under water. The city remained flooded for five years.
• 1697 – The Treaty of Rijswijk is signed by England, Spain, the Holy Roman Empire, the United Provinces and France, ending the War of the Grand Alliance or Nine Years' War.
• 1776 – In New Orleans, the Spanish governor Luis de Unzaga y Amézaga receives authorization from Charles III to allow free trade with ships of the Thirteen Colonies, which were fighting for their independence.
• 1796 – Death of Juan José Delhuyar, Spanish chemist (b. 1754).
• 1816 – At the Spanish-speaking town of San Francisco de Borja, Guaraní soldiers of commander Andresito Guazurarí, following the Portuguese-Brazilian invasion of 1816, lay siege to the town (occupied by Portuguese and Brazilian forces since 1801).
• 1836 – In Spain, the Battle of Villarrobledo takes place during the First Carlist War.
• 1845 – The Italian mercenary Giuseppe Garibaldi and his legion of "virtuous plunderers" (during the Guerra Grande (1838-1852) of Brazil, France and Great Britain against Juan Manuel de Rosas) land at the town of Gualeguaychú (Entre Ríos Province), an Argentine logistics center 200 km north of Buenos Aires, and plunder its inhabitants.
• 1880 – In Argentina, the city of Buenos Aires is declared capital of the Republic and separated from provincial jurisdiction.
• 1893 – Birth of Heraclio Alfaro Fournier, Spanish engineer and aviator (d. 1962).
• 1904 – Death of José María Yermo y Parres, Mexican priest (b. 1851).
• 1920 – Lieutenant Colonel José Millán Astray founds the Tercio de Extranjeros or Spanish Legion.
• 1970 – Death of Arturo Rosenblueth Stearns, Mexican researcher, physician and physiologist (b. 1900).
• 1984 – In Argentina, the National Commission on the Disappearance of Persons delivers its report Nunca más (with data on the crimes against humanity of the Videla dictatorship) to President Raúl Alfonsín.
• 2009 – In Havana (Cuba), the second edition of the Paz sin Fronteras concert is held before more than a million people.
• 2017 – On the island of Puerto Rico, Hurricane Maria leaves 3,000 dead.