Births on December 31

Enrique Maier, Spanish tennis player (d. 1981)

Enrique 'Bubi' Maier (December 31, 1910 – August 22, 1981) was a male Spanish tennis player who was mainly active in the 1930s.

11 May

Glacier National Park (U.S.)
An act of the U.S. Congress establishes Glacier National Park in Montana.
4 Jul

Jack Johnson (boxer)
African-American boxer Jack Johnson knocks out white boxer Jim Jeffries in a heavyweight boxing match, sparking race riots across the United States.
15 Jul

Alzheimer's disease
In his book Clinical Psychiatry, Emil Kraepelin gives a name to Alzheimer's disease, naming it after his colleague Alois Alzheimer.
18 Sep

Suffrage
In Amsterdam, 25,000 demonstrate for general suffrage.
7 Nov

Wright brothers
The first air freight shipment (from Dayton, Ohio, to Columbus, Ohio) is undertaken by the Wright brothers and department store owner Max Moorehouse.