Later, in Shanksville, Pa., Vice President Kamala Harris and former President George W. Bush talked of courage, resilience and unity.

All but four of the 19 hijackers on 9/11 were Saudi citizens and the Saudi kingdom was the birthplace of Osama bin Laden, the head of al-Qaida and mastermind of the attack

The terrorist attacks on the United States nearly 20 years ago brought profound change in America and the world.

While the Sept. 11 attacks united much of America in grief and anger, conspiracy theories about what happened that day uncovered a well of distrust.