Citizens of Montenegro voted by 55.5-45.5% on May 21, 2006 to secede from the State Union of Serbia and Montenegro and declare independence. The new country formally declared independence on June 3 of that year. Learn more about the 2006 Montenegro independence referendum.

English prison reformer Elizabeth Fry was born on May 21, 1780. Learn more about Elizabeth Fry.

On May 21, 1881, Clara Barton founded the American Red Cross. Read the Congressional Charter of the American Red Cross and learn more about the history of the organization.