The temperature on January 21, 1911 was between -2.9 °C and 0.3 °C and averaged -1.5 °C. There was 0.2 mm of rain. The average windspeed was 2 Bft (weak wind) and was prevailing from the south. Source: KNMI
January 26 » Glenn Curtiss flies the first successful American seaplane.
May 21 » President of Mexico Porfirio Díaz and the revolutionary Francisco Madero sign the Treaty of Ciudad Juárez to put an end to the fighting between the forces of both men, concluding the initial phase of the Mexican Revolution.
July 4 » A massive heat wave strikes the northeastern United States, killing 380 people in eleven days and breaking temperature records in several cities.
September 23 » Pilot Earle Ovington makes the first official airmail delivery in America under the authority of the United States Post Office Department
October 9 » An accidental bomb explosion triggers the Wuchang Uprising against the Chinese monarchy.
October 13 » Prince Arthur, Duke of Connaught and Strathearn, becomes the first Governor General of Canada of royal descent.
When copying data from this family tree, please include a reference to the origin: John Bart, "Family tree Denneman", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-denneman/I756.php : accessed February 16, 2026), "Johannes Cornelis Denneman (1911-)".
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