July 31 is a surprisingly geeky day.
- 1498 – On his third voyage to the Western Hemisphere, Christopher Columbus becomes the first European to discover the island of Trinidad.
- 1588 – The Spanish Armada is spotted off the coast of England.
- 1703 – Daniel Defoe is placed in a pillory for the crime of seditious libel after publishing a politically satirical pamphlet, but is pelted with flowers.
- 1777 – The U.S. Second Continental Congress passes a resolution that the services of Marquis de Lafayette “be accepted, and that, in consideration of his zeal, illustrious family and connexions, he have the rank and commission of major-general of the United States.”
- 1865 – The first narrow gauge mainline railway in the world opens at Grandchester, Australia.
- 1930 – The radio mystery program The Shadow is aired for the first time.
- 1971 – Apollo program: Apollo 15 astronauts become the first to ride in a lunar rover.
- 1976 – Viking program: Viking 1 – NASA releases the famous Face on Mars photo.
- 1999 – Discovery Program: Lunar Prospector – NASA intentionally crashes the spacecraft into the Moon, thus ending its mission to detect frozen water on the moon’s surface.
- 1704 – Gabriel Cramer, Swiss mathematician (d. 1752)
- 1718 – John Canton, English physicist (d. 1772)
- 1724 – Noël François de Wailly, French lexicographer (d. 1801)
- 1803 – John Ericsson, Swedish inventor and engineer (d. 1889)
- 1835 – Paul du Chaillu, French explorer (d. 1903)
- 1858 – Richard Dixon Oldham, British geologist (d. 1936)
- 1918 – Paul D. Boyer, American chemist, Nobel Prize Laureate
- 1919 – Primo Levi, Italian author and chemist (d. 1987)
- 1944 – Robert C. Merton, American mathematician
- 1965 – J.K. Rowling, English author.
- 1966 – Dean Cain, American actor
- 1726 – Nicolaus II Bernoulli, Swiss mathematician (b. 1695)
- 1875 – Andrew Johnson, 17th President of the United States (b. 1808)
- 1980 – Pascual Jordan, German physicist (b. 1902)