11th International Botanical Congress
On August 23, 1969, the US Post Office issued a set of four stamps for the 11th International Botanical Congress (IBC).
Science
First International Polar Year
On August 1, 1882, the first International Polar Year (IPY) began.
First Heat-Sensitive Stamp
On June 20, 2017, the USPS issued the first-ever heat sensitive stamp, honoring the total solar eclipse that occurred later that year.
Launch of Pioneer 11
On April 5, 1973 (some sources cite April 6 UTC (Coordinated Universal Time), the Pioneer 11 space probe launched from Cape Canaveral, Florida.
First Light of the Hale Telescope
On January 26, 1949, the Hale Telescope at Palomar Observatory first saw light. Still in use today, the Hale telescope is one of the world’s largest optical telescopes.
First Americans Sight Antarctica
On November 17, 1820, Nathaniel Palmer and his crew became the first Americans to see Antarctica.
Birth of Benjamin Banneker
Benjamin Banneker was born on November 9, 1731, in Baltimore County, Maryland.
Birth of Florence Nightingale
Nurse and social reformer Florence Nightingale was born on May 12, 1820, in Florence, Tuscany, Italy.
Soviet-Canadian Polar Bridge Expedition
On April 25, 1988, the Soviet-Canadian Polar Bridge Expedition reached the North Pole.