1. On September 17, 1791, the United States Congress approved the creation of a new national capital city in the District of Columbia, which would later become Washington D.C.

2. On September 17, 1862, during the American Civil War, the Battle of Antietam took place in nearby Sharpsburg, Maryland. It remains the deadliest one-day battle in American history with over 22,000 casualties.

3. September 17, 1916, marked the opening of the National Park Service Organic Act, which created the National Park Service in the District of Columbia as well as in other states.

4. On September 17, 2001, just six days after the 9/11 attacks, the District of Columbia’s National Guard was mobilized as part of a larger effort to secure the city and nation from further attacks.

5. September 17, 2011, marked the opening of the National Museum of African American History and Culture in Washington D.C, which became the 19th museum in the Smithsonian Institution and the only national museum solely dedicated to African American history and culture.