1. On December 10, 1801, the District of Columbia was officially incorporated as a municipality. Prior to this, it had been governed by a board of commissioners appointed by the President of the United States.

2. In 1869, the cornerstone was laid for the new headquarters of the United States Department of Justice. Located on Pennsylvania Avenue, the building was the first federal building to use electricity for lighting.

3. In 1934, the National Zoo in Washington D.C. welcomed a new resident: a giant panda named Su-Lin. She was a gift from the Chinese government and was the first panda to be exhibited outside of China.

4. December 10, 1953, marked the debut of the National Christmas Tree on the Ellipse in Washington D.C. President Dwight D. Eisenhower lit the tree, which was decorated with 2,500 electric bulbs, and the tradition has continued every year since.

5. In 2009, the D.C. Council voted unanimously to legalize same-sex marriage, becoming the sixth place in the United States to do so. The law went into effect on March 3, 2010, and paved the way for marriage equality across the country.