January 31 » Czechoslav Trade Union Association is founded in Prague.
April 30 » J. J. Thomson of the Cavendish Laboratory announces his discovery of the electron as a subatomic particle, over 1,800 times smaller than a proton (in the atomic nucleus), at a lecture at the Royal Institution in London.
July 26 » Anglo-Afghan War: The Pashtun fakir Saidullah leads an army of more than 10,000 to begin a siege of the British garrison in the Malakand Agency of the North West Frontier Province of India.
August 10 » German chemist Felix Hoffmann discovers an improved way of synthesizing acetylsalicylic acid (aspirin).
December 6 » London becomes the world's first city to host licensed taxicabs.
December 9 » Activist Marguerite Durand founds the feminist daily newspaper La Fronde in Paris.
Day of marriage September 15, 1920
The temperature on September 15, 1920 was between 7.0 °C and 15.2 °C and averaged 12.9 °C. There was 2.6 mm of rain. The average windspeed was 3 Bft (moderate breeze) and was prevailing from the south-southwest. Source: KNMI
In The Netherlands , there was from September 9, 1918 to September 18, 1922 the cabinet Ruys de Beerenbrouck I, with Jonkheer mr. Ch.J.M. Ruys de Beerenbrouck (RKSP) as prime minister.
January 7 » The New York State Assembly refuses to seat five duly elected Socialist assemblymen.
January 8 » The steel strike of 1919 ends in failure for the Amalgamated Association of Iron, Steel and Tin Workers labor union.
January 16 » Zeta Phi Beta Sorority Incorporated was founded on the campus of Howard University.
January 26 » Former Ford Motor Company executive Henry Leland launches the Lincoln Motor Company which he later sold to his former employer.
February 10 » About 75% of the population in Zone I votes to join Denmark in the 1920 Schleswig plebiscites.
April 23 » The Grand National Assembly of Turkey (TBMM) is founded in Ankara. The assembly denounces the government of Sultan Mehmed VI and announces the preparation of a temporary constitution.
Day of death August 21, 1975
The temperature on August 21, 1975 was between 14.3 °C and 23.4 °C and averaged 17.2 °C. There was 20.9 mm of rain during 4.2 hours. There was 2.3 hours of sunshine (16%). The heavily clouded was. The average windspeed was 1 Bft (weak wind) and was prevailing from the east-northeast. Source: KNMI
In The Netherlands , there was from Friday, May 11, 1973 to Monday, December 19, 1977 the cabinet Den Uyl, with Drs. J.M. den Uyl (PvdA) as prime minister.
When copying data from this family tree, please include a reference to the origin: Marieke Cooper, "Family tree Cooper, Kooper, Oostwal, Robert, Ooteman en Blokland", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-cooper/I2201.php : accessed January 6, 2026), "Pieter Bernardus Kooper (1897-1975)".
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