Today in History....December 6

* 1768, the first edition of the Encyclopedia Britannica is published

* 1790, the U.S. Congress moves from New York City to Philadelphia

* 1884, the Washington Monument in Washington D.C. is completed

* 1897, London becomes the world's first city to host licensed taxis

* 1907, the worst mining disaster in U.S. history occurred as 362 men and boys died in a coal mine explosion in Monongah, W.Va.

* 1917, some 2,000 people died when an explosives-laden French cargo ship collided with a Norwegian vessel at the harbor in Halifax, Nova Scotia, setting off a blast that devastated the city

* 1922, one year to the day after the signing of the Anglo-Irish Treaty, the Irish Free State comes into existence

* 1956, a water polo match between Hungary and the USSR takes place during the 1956 Summer Olympics in Melbourne, representative of the 1956 Hungarian Revolution

* 1973, House Minority Leader Gerald R. Ford was sworn in as vice president, succeeding Spiro T. Agnew

* 2005, several villagers are shot dead during protests in Dongzhou, China.

* 2006, NASA reveals photographs taken by Mars Global Surveyor suggesting the presence of liquid water on Mars.