On September 11, 1927, the 15th Zionist Congress concluded in Basel, having met at the Stadtcasino from August 30 through September 11 of that year. This closing day marked the end of a gathering documented in the official protocols of the congress. See wikipedia for more information.

On September 11, 2001, coordinated terrorist attacks by al-Qaeda struck the United States, targeting the World Trade Center in New York and the Pentagon in Washington, D.C., while a fourth hijacked plane crashed in Pennsylvania after passengers resisted. Nearly 3,000 people were killed, making it the deadliest terrorist attack in history and a defining moment in global politics and security. See wikipedia for more information.