1. In 1802, the District of Columbia was officially incorporated as a city. April 1st marked the beginning of a new government, with Thomas Jefferson appointing Benjamin B. French as the first mayor of the city.

2. On April 1, 1862, during the American Civil War, the Confederate Army under General Jubal Early attacked Fort Stevens, which protected the northern boundary of Washington, DC. President Abraham Lincoln even traveled to the fort to observe the skirmish.

3. In 1918, during World War I, the War Savings Committee launched a campaign in Washington, DC, to encourage citizens to buy bonds to support the war effort. Dubbed "April Fools' Bond Day," the campaign included a parade and a performance by a 500-member band.

4. On April 1, 1968, the U.S. Congress passed the District of Columbia Home Rule Act, giving the city limited self-governance. The act established a mayor and council, and granted the city budgetary autonomy and control over its own laws.

5. In 1971, the Washington DC metro system began operations on April 1, with five stations along the Red Line opening to the public. The system has since expanded to include six lines and over 90 stations, connecting the District of Columbia to neighboring Maryland and Virginia.