December 1, 1913
- The Ford Motor Company introduces the first moving assembly line.
December 1, 1959
- Opening date for signature of the Antarctic Treaty, which sets aside Antarctica as a scientific preserve and bans military activity on the continent.
December 1, 1975
- Lambda Theta Phi - The first Latino fraternity is established in New Jersey.
December 2, 1942
- Manhattan Project: A team led by Enrico Fermi initiates the first self-sustaining nuclear chain reaction.
December 3, 1917
- After nearly 20 years of planning and construction, including two collapses causing 89 deaths, the Quebec Bridge opens to traffic.
December 4, 1674
- Father Jacques Marquette founds a mission on the shores of Lake Michigan to minister to the Illiniwek.
December 5, 1492
- Christopher Columbus becomes the first European to set foot on the island of Hispaniola, now Haiti and the Dominican Republic.
December 6, 1865
- The Thirteenth Amendment to the United States Constitution is ratified, banning slavery.
December 6, 1921
- The Anglo-Irish Treaty is signed in London by British and Irish representatives.
December 7, 1787
- Delaware becomes the first state to ratify the United States Constitution.
December 8, 1980
- John Lennon, an English musician and peace activist, is murdered by Mark David Chapman, a mentally unstable fan, in front of The Dakota apartment building in New York City.
December 8, 1991
- The leaders of Russia, Belarus and Ukraine sign an agreement dissolving the Soviet Union and establishing the Commonwealth of Independent States.
December 9, 1851
- The first YMCA in North America is established in Montreal, Quebec.
December 10, 1948
- The UN General Assembly adopts the Universal Declaration of Human Rights.
December 11, 1946
- The United Nations International Children's Emergency Fund is established.
December 12, 1787
- Pennsylvania becomes the second state to ratify the United States Constitution five days after Delaware became the first.
December 14, 1911
- Roald Amundsen's team, comprising himself, Olav Bjaaland, Helmer Hanssen, Sverre Hassel, and Oscar Wisting, becomes the first to reach the South Pole.
December 14, 2004
- The Millau viaduct, the tallest bridge in the world, near Millau, France is officially opened.
December 15, 1906
- The London Underground's Great Northern, Piccadilly and Brompton Railway opens.
December 15, 1970
- Soviet spacecraft Venera 7 successfully land on Venus. It is the first successful soft landing on another planet
December 16, 1997
- An episode of Pokémon, "Dennō Senshi Porygon", aired in Japan induces seizures in 685 Japanese children.
December 17, 1903
- The Wright Brothers make their first powered and heavier-than-air flight in the «Wright Flyer» at Kitty Hawk, North Carolina.
December 17, 1989
- The first episode of television series The Simpsons, "Simpsons Roasting on an Open Fire", airs in the United States.
December 18, 1787
- New Jersey becomes the third state to ratify the U.S. Constitution.
December 18, 1888
- Richard Wetherill and his brother in-law discover the ancient Indian ruins of Cliff Palace in Mesa Verde.
December 18, 1958
- Project SCORE, the world's first communications satellite, is launched.
December 19, 1983
- The original FIFA World Cup trophy, the Jules Rimet Trophy, is stolen from the headquarters of the Brazilian Football Confederation in Rio de Janeiro.
December 20, 1860
- South Carolina becomes the first state to secede from the United States.
December 20, 1951
- The EBR-1 in Arco, Idaho becomes the first nuclear power plant to generate electricity.
December 20, 2004
- A gang of thieves steal £26.5 million worth of currency from the Donegall Square West headquarters of Northern Bank in Belfast,
December 21, 1891
- The first game of basketball ever played took place in the Mason Square district of Springfield.
December 21, 1898
- Radium was discovered by Marie Skłodowska-Curie and her husband Pierre.
December 21, 1913
- Arthur Wynne's "word-cross", the first crossword puzzle, is published in the New York World.
December 22, 1790
- The Turkish fortress of Izmail is stormed and captured by Suvorov and his Russian armies.
December 22, 1989
- Berlin's Brandenburg Gate re-opens after nearly 30 years, effectively ending the division of East and West Germany.
December 23, 1913
- The Federal Reserve Act is signed into law by President Woodrow Wilson, creating the Federal Reserve.
December 23, 1972
- The 16 survivors of the Andes flight disaster are rescued after 73 days, having survived by cannibalism.
December 25, 274
- Emperor Aurelian makes Sol Invictus to an official cult, it becomes the state religion of Rome.
December 26, 1870
- The 12.8-km long Fréjus Rail Tunnel through the Alps is completed.
December 26, 1991
- The Supreme Soviet of the Soviet Union meets and formally dissolves the USSR.
December 26, 2004
- A 9.3 magnitude earthquake creates a tsunami causing devastation in Sri Lanka.
December 27, 1922
- Japanese aircraft carrier Hōshō becomes the first purpose built aircraft carrier to be commissioned in the world.
December 28, 1895
- The Lumière brothers perform for their first paying audience at the Grand Cafe in Boulevard des Capucines, marking the debut of the cinema.
December 28, 1908
- A magnitude 7.2 earthquake rocks Messina, Sicily killing over 75,000.
December 29, 1835
- The Treaty of New Echota is signed, ceding all the lands of the Cherokee east of the Mississippi River to the United States.
December 29, 1845
- According with International Boundary delimitation, U.S.A annexes the Mexican state of Texas, following the Manifest Destiny doctrine. For others, the Republic of Texas, which had been independent since the Texas Revolution of 1836, is admitted as the 28th U.S. state.
December 31, 1879
- Thomas Edison demonstrates incandescent lighting to the public for the first time, in Menlo Park, New Jersey.