1. In 1804, the Lewis and Clark Expedition arrived in the District of Columbia. The explorers had set off from St. Louis the previous year on an expedition to explore the newly acquired Louisiana Territory and find a route to the Pacific Ocean.

2. In 1865, the 13th Amendment to the United States Constitution was ratified by Georgia, becoming the 27th state to do so. This amendment abolished slavery and involuntary servitude, except as punishment for a crime.

3. In 1926, the first international radio broadcast was transmitted from Washington, D.C. The program was a concert by the U.S. Navy Band and was heard in Canada and Europe.

4. In 1952, the first ever hydrogen bomb was detonated at Eniwetok Atoll in the Pacific Ocean. The bomb, known as "Ivy Mike," was designed and built at the Lawrence Livermore National Laboratory in California, but was tested in the District of Columbia.

5. In 1973, the District of Columbia Home Rule Act was signed into law, granting local government autonomy to the city. Before this, Washington, D.C. had been governed by a federally appointed commission. The new system established a mayor and city council to govern the city and make local laws.