1937: J.R.R. Tolkien's "The Hobbit" is published.
1964: Malta gains independence from the United Kingdom.
1972: Ferdinand Marcos declares martial law in the Philippines, marking the beginning of his authoritarian regime.
1981: Belize gains independence from the United Kingdom.
2001: Terrorist attacks on the World Trade Center and the Pentagon occur, killing nearly 3,000 people. This event significantly shapes global politics and leads to the War on Terror.
2013: The Westgate shopping mall in Nairobi, Kenya, is attacked by al-Shabaab militants, resulting in the death of dozens of people.
2015: Pope Francis visits the United States and addresses a joint session of Congress, becoming the first pope to do so.
These are just a few examples of notable events that took place on September 21st throughout history.