December 1: In Montgomery, Alabama, Rosa Parks refuses to obey bus driver James F. Blake's order that she give up her seat to make room for a white passenger and is arrested, leading to the Montgomery bus boycott.

December 4: The International Federation of Blood Donor Organizations was founded in Luxembourg.

December 5: The American Federation of Labor and the Congress of Industrial Organizations merge to become the AFL-CIO. - The Montgomery Improvement Association is formed in Montgomery, Alabama, by Dr. Martin Luther King, Jr., and other Black ministers to coordinate a Black people's boycott of all city buses.

December 9: Adnan Menderes of DP forms the new government of Turkey (22nd government)

December 14: The Tappan Zee Bridge in New York opens to traffic. - Albania, Austria, Bulgaria, Cambodia, Finland, Hungary, Ireland, Italy, Jordan, Laos, Libya, Nepal, Portugal, Romania, Spain, and Sri Lanka join the United Nations simultaneously, after several years of moratorium on admitting new members that began during the Korean War.

December 20: Cardiff is declared by the British Government as the capital of Wales.

December 22: American cytogeneticist Joe Hin Tjio discovers the correct number of human chromosomes, forty-six.

December 31: General Motors Corporation becomes the first American corporation to make a profit of over one billion dollars in one year. (source: Wikipedia)