Wikipedia:Selected anniversaries/December 20
- 1803 - As part of the Louisiana Purchase, New Orleans was transfered from France to the United States.
- 1860 - South Carolina seceded from the United States, leading to the American Civil War.
- 1995 - NATO began peacekeeping in Bosnia.
- 1999 - Portugal transferred sovereignty of Macau to the People's Republic of China.
Recent days: December 19 – December 18 – December 17