December 1 ( ):
- 1991 – Ukraine citizens, by a 9–1 margin, voted in support of secession from the Soviet Union.
- 2000 – Vicente Fox became Mexico's first opposition-party president since 1910, ending the 71-year dominance of the Institutional Revolutionary Party.
December 2 ():
- 1832 – US President James Monroe introduced the Monroe Doctrine, claiming the right to respond militarily to any further European intervention in the Western Hemisphere.
December 3 ():
- 1818 – Illinois becomes the 21st U.S. state.
- 1964 – Berkeley Free Speech Movement: Police arrest over 800 students at the University of California, Berkeley, following their takeover and sit-in at the administration building in protest at the UC Regents' decision to forbid protests on UC property.
- 1967 – At Groote Schuur Hospital in Cape Town, South Africa, a transplant team headed by Christiaan Barnard carries out the first heart transplant on a human (53-year-old Louis Washkansky).
- 1984 – Bhopal Disaster: A methyl isocyanate leak from a Union Carbide pesticide plant in Bhopal, India, kills more than 3,800 people outright and injures 150,000–600,000 others (some 6,000 of whom would later die from their injuries) in one of the worst industrial disasters in history.
- 1989 – Cold War: In a meeting off the coast of Malta, US President George H. W. Bush and Soviet leader Mikhail Gorbachev release statements indicating that the cold war between Nato and The Soviet Union may be coming to an end.
- 1992 – UN Security Council Resolution 794 is unanimously passed, approving a coalition of United Nations peacekeepers led by the United States to form UNITAF, with the task of establishing peace and ensuring that humanitarian aid is distributed in Somalia.
- 1997 – In Ottawa, Canada, representatives from 121 countries sign The Ottawa treaty prohibiting manufacture and deployment of anti-personnel landmines. The United States, People's Republic of China, and Russia do not sign the treaty, however.
December 4 ():
- 1619 – 38 colonists from Berkeley Parish in England disembark in Virginia and give thanks to God (this is considered by many to be the first Thanksgiving in the Americas).
- 1674 – Father Jacques Marquette founds a mission on the shores of Lake Michigan to minister to the Illiniwek (the mission would later grow into the city of Chicago, Illinois).
- 1875 – Notorious New York City politician Boss Tweed escapes from prison and flees to Cuba, then Spain.
- 1881 – The first edition of the Los Angeles Times is published.
- 1943 – World War II: U.S. President Franklin D. Roosevelt closes down the Works Progress Administration, because of the high levels of wartime employment in the United States.
- 1945 – By a vote of 65 to 7, the United States Senate approves United States participation in the United Nations (the UN is established on October 24, 1945).
- 1954 – The first Burger King is opened in Miami, Florida, United States
- 1982 – The People's Republic of China adopts its current constitution.
December 5 ():
- 1933 – The 21st Amendment to the Constitution was ratified, repealing the 18th Amendment and ending Prohibition.
December 6 ():
- 1922 – The Irish Free State came into existence as a Dominion of the United Kingdom, following the Anglo-Irish Treaty that ended the Irish War of Independence.
December 7 ():
- 1941 – Under trade and military pressure from US President Franklin D. Roosevelt, Japan launched a preemptive attack on Pearl Harbor.
December 8 ():
December 9 ():
- 1793 – New York City's first daily newspaper, the American Minerva, is established by Noah Webster.
- 1835 – The Texian Army captures San Antonio, Texas.
- 1851 – The first YMCA in North America is established in Montreal, Quebec.
- 1861 – American Civil War: The Joint Committee on the Conduct of the War is established by the U.S. Congress.
- 1872 – In Louisiana, P. B. S. Pinchback becomes the first serving African-American governor of a U.S. state.
- 1875 – The Massachusetts Rifle Association, "America's Oldest Active Gun Club", is founded.
- 1946 – The "Subsequent Nuremberg Trials" begin with the "Doctors' Trial", prosecuting doctors alleged to be involved in human experimentation.
- 1950 – Harry Gold is sentenced to 30 years in jail for helping Klaus Fuchs pass information about the Manhattan Project to the Soviet Union. His testimony is later instrumental in the prosecution of Julius and Ethel Rosenberg.
- 1953 – Red Scare: General Electric announces that all communist employees will be discharged from the company.
- 1958 – The John Birch Society is founded in the United States.
- 1979 – The eradication of the smallpox virus is certified, making smallpox the first and to date only human disease driven to extinction.
- 2000 – The Supreme Court of the United States stays the sixth Florida recount.
- 2008 – The Governor of Illinois, Rod Blagojevich, is arrested by federal officials for a number of alleged crimes including attempting to sell the United States Senate seat being vacated by President-elect Barack Obama's election to the Presidency.
December 10 ():
- 1690 – Massachusetts issued the first government paper money in the Western world.
- 1832 – President Andrew Jackson decried South Carolina's Ordinance of Nullification, prompting replies from Abel P. Upshur and Littleton Waller Tazewell.
December 11 ():
- 1997 – The Kyoto Protocol was adopted, with the intention of reducing the production of greenhouse gases in certain countries.
December 12 ():
- 1805 – Abolitionist William Lloyd Garrison was born.
- 1941 – Blaming the Jews for World War II, Adolf Hitler declared the imminent destruction of the Jewish race.
December 13 ():
- 1636 – The Massachusetts Bay Colony organizes three militia regiments to defend the colony against the Pequot Indians. This organization is recognized today as the founding of the United States National Guard.
- 1862 – American Civil War: At the Battle of Fredericksburg, Confederate General Robert E. Lee defeats the Union Major General Ambrose E. Burnside.
- 1949 – The Knesset votes to move the capital of Israel to Jerusalem.
- 1972 – Apollo program: Eugene Cernan and Harrison Schmitt begin the third and final Extra-vehicular activity (EVA) or "Moonwalk" of Apollo 17. This is the last manned mission to the moon of the 20th century.
- 1981 – General Wojciech Jaruzelski declares martial law in Poland to prevent dismantling of the communist system by Solidarity.
- 2003 – Former Iraqi President Saddam Hussein is captured near his home town of Tikrit (see Operation Red Dawn).
December 14 ():
- 1751 – The Theresian Military Academy is founded as the first Military Academy in the world.
- 1819 – Alabama becomes the 22nd U.S. state.
- 1825 – Advocates of Liberalism in Russia rise up against Tsar Nicholas I and are put down in the Decembrist Revolt in St. Petersburg.
- 1903 – The Wright brothers make their first attempt to fly with the Wright Flyer at Kitty Hawk, North Carolina.
- 1946 – The United Nations General Assembly votes to establish its headquarters in New York City.
- 1947 – The National Association for Stock Car Auto Racing (NASCAR) is founded in Daytona Beach, Florida.
- 1964 – American Civil Rights Movement: Heart of Atlanta Motel v. United States – The United States Supreme Court rules that the U.S. Congress can use the Constitution's Commerce Clause power to fight discrimination.
- 1972 – Apollo program: Eugene Cernan is the last person to walk on the moon, after he and Harrison Schmitt complete the third and final Extra-vehicular activity (EVA) of the Apollo 17 mission. This is the last manned mission to the moon of the 20th century.
- 2008 – President George W. Bush makes his fourth and final (planned) trip to Iraq as president and is almost struck by two shoes thrown at him by Iraqi journalist Muntadhar al-Zaidi during a news conference in Baghdad.
December 15 ():
- 1791 – The ten amendments to the Constitution known as the Bill of Rights were officially ratified, purporting to protect the rights of the people and limit the power of the federal government.
- 1815 – Several New England states sent delegates to the Hartford Convention to discuss ways to protest the War of 1812 and end unconstitutional trade restrictions.
December 16 ():
- 1689 – The Parliament of England ratified the English Bill of Rights, recognizing certain individual rights and limiting the power of the monarch.
- 1773 – American colonists in Boston boarded three British ships and threw tea overboard in protest of the Tea Act.
December 17 ():
- 1997 – In the United Kingdom, legislation went into effect banning virtually all handguns, even those used by the country's olympic competitive shooting team.
December 18 ():
- 1941 – The War Powers Act of 1941 was enacted, giving President Franklin D. Roosevelt numerous powers, including censorship of mail and opening of census records.
December 19 ():
- 1828 – The South Carolina Exposition and Protest, written by John C. Calhoun in response to the tariff of 1828, was presented to the South Carolina House of Representatives.
December 20 ():
- 1860 – South Carolina became the first of eleven states to secede from the United States and eventually form the Confederate States of America.
December 21 ():
- 1798 – The Virginia Resolutions of 1798, protesting the Alien and Sedition Acts, were passed by the Virginia House of Delegates.
December 22 ():
- 1807 – The Embargo Act, forbidding trade with all foreign countries, is passed by the U.S. Congress, at the urging of President Thomas Jefferson.
- 1809 – The Non-Intercourse Act, lifting the Embargo Act except for the United Kingdom and France, is passed by the U.S. Congress.
- 1851 – The first freight train is operated in Roorkee, India.
- 1920 – The GOELRO economic development plan is adopted by the 8th Congress of Soviets of the Russian SFSR.
- 1937 – The Lincoln Tunnel opens to traffic in New York City.
- 1942 – World War II: Adolf Hitler signs the order to develop the V-2 rocket as a weapon.
- 1964 – First flight of the SR-71 (Blackbird).
- 1978 – The pivotal Third Plenum of the 11th National Congress of the Communist Party of China is held in Beijing, with Deng Xiaoping reversing Mao-era policies to pursue a program for Chinese economic reform.
- 1989 – Berlin's Brandenburg Gate re-opens after nearly 30 years, effectively ending the division of East and West Germany.
- 2001 – Richard Reid attempts to destroy a passenger airliner by igniting explosives hidden in his shoes aboard American Airlines Flight 63.
- 2010 – The repeal of the Don't Ask Don't Tell policy, the 17-year-old policy banning on homosexuals serving openly in the United States military, is signed into law by President Barack Obama.
December 23 ():
- 1913 – President Woodrow Wilson signed the Federal Reserve Act, establishing the Federal Reserve System.
December 24 ():
- 1814 – The Treaty of Ghent is signed ending the War of 1812.
- 1851 – Library of Congress burns.
- 1865 – The Ku Klux Klan is formed.
- 1906 – Radio: Reginald Fessenden transmits the first radio broadcast; consisting of a poetry reading, a violin solo, and a speech.
- 1924 – Albania becomes a republic.
- 1943 – World War II: U.S. General Dwight D. Eisenhower becomes the Supreme Allied Commander.
- 1968 – Apollo Program: The crew of Apollo 8 enters into orbit around the Moon, becoming the first humans to do so. They performed 10 lunar orbits and broadcast live TV pictures that became the famous Christmas Eve Broadcast, one of the most watched programs in history.
- 1973 – District of Columbia Home Rule Act is passed, allowing residents of Washington, D.C. to elect their own local government.
December 25 ():
- 1914 – In the Christmas truce, German and British troops on the Western Front of World War I temporarily ceased fire.
December 26 ():
December 27 ():
- 1945 – The World Bank and IMF were created with the signing of an agreement by 29 nations.
- 1979 – The Soviet Union invaded Afghanistan, beginning a nine-year conflict.
December 28 ():
- 1832 – John C. Calhoun resigned his position as Vice President of the United States, in the midst of the Nullification Crisis.
- 1895 – The Lumière brothers performed for their first paying audience at the Grand Cafe in Boulevard des Capucines, marking the debut of the cinema.
- 1973 – The Endangered Species Act was enacted in the United States.
December 29 ():
- 1845 – The United States admitted the Republic of Texas as the 28th US state, despite Mexican refusal to recognize the independence of Texas after the Texas Revolution of 1836.
- 1911 – Mongolia gained independence from the Qing dynasty.
December 30 ():
- 1853 – The United States bought land from Mexico to facilitate railroad building in the Southwest.
- 1922 – The Union of Soviet Socialist Republics was formed.
- 1936 – The United Auto Workers union staged its first sit-down strike.
- 2006 – Saddam Hussein, former Iraqi dictator, was executed for war crimes.
December 31 ():
- 1965 – Time magazine, with John Maynard Keynes on the cover, quoted Milton Friedman as saying, "We are all Keynesians now."