1. In 1864, the Union League Club of the District of Columbia was founded. This was a political organization that supported the Union during the Civil War and advocated for African American rights.

2. On May 21, 1881, Clara Barton founded the American Red Cross in Washington D.C. The organization still helps people in need across the country and the world today.

3. The first ever National Conference on Citizenship was held in Washington D.C. on May 21, 1941. The conference brought together leaders from various industries to discuss issues related to citizenship and civic participation.

4. The Lincoln Memorial Reflecting Pool was dedicated on May 21, 1923. The pool, which is over 2,000 feet long, is often used as a backdrop for photographs of the Washington Monument and the Lincoln Memorial.

5. The Capital Crescent Trail, a popular walking and biking trail in the D.C. area, officially opened on May 21, 1994. The trail runs over 11 miles from Georgetown to Silver Spring, Maryland and provides a scenic route for commuters and outdoor enthusiasts alike.