February 21st
1554 – Death of Hieronymus Bock, German botanist
1721 – Birth of John McKinly, American physician
1895 – Birth of Carl Peter Henrik Dam Danish biochemist, Nobel laureate
1901 – Death of George Francis FitzGerald, Irish mathematician
1918 – The last Carolina parakeet dies in captivity at the Cincinnati Zoo.
1926 – Death of Heike Kamerlingh Onnes, Dutch physicist, Nobel Prize laureate
1938 – Death of George Ellery Hale, American astronomer
1953 – Francis Crick and James D. Watson discover the structure of DNA.
1968 – Death of Howard Walter Florey, Australian-born pharmocologist, recipient of the Nobel Prize in Physiology or Medicine
1999 – Death of Gertrude B. Elion, American scientist, recipient of the Nobel Prize in Physiology or Medicine
2002 – Death of Harold Furth, Austrian-born physicist