1. In 1790, the United States Supreme Court held its first session in New York City, which was then the capital of the United States. This event marked the beginning of the nation's highest court, which has since moved to its current location in Washington, D.C.

2. In 1861, just before the start of the Civil War, the Peace Convention of 1861 was held in Washington, D.C. The convention aimed to establish a compromise between the North and South, but ultimately failed to prevent the war from breaking out.

3. In 1871, the District of Columbia became the first jurisdiction in the United States to grant African American men the right to vote. This was a significant step forward for civil rights in the nation's capital.

4. In 1893, the National Zoo in Washington, D.C. opened its doors to the public for the first time. The zoo, which is now part of the Smithsonian Institution, has since become a popular attraction for visitors to the nation's capital.

5. In 1960, four black college students held a sit-in at the Woolworth's lunch counter in Greensboro, North Carolina to protest segregation. This event sparked a wave of similar protests across the country, including in Washington, D.C., and helped to fuel the civil rights movement of the 1960s.