Ground Zero, the site of the Sept. 11, 2001, attacks by Al Qaeda that felled the World Trade Center's Twin Towers, has turned into a rallying site since New Yorkers learned the Al Qaeda leader was killed Sunday during a raid by U.S. Navy SEALs.
Former President George W. Bush also notably visited the site in the days after the attacks in 2001, gave his memorable speech by megaphone to emergency workers.
Obama addressed members of Congress at the White House Monday and said he felt the “same sense of unity as 9/11.” He also thanked the heroes who carried out the mission.
"I know that unity that we felt on 9/11 has frayed a little bit over the years, and I have no illusions about the difficulties, the debates we'll have to be engaged in in the weeks and months to come," Obama said. "But I also know there have been several moments like this during the course of this year that have brought us together as an American family, whether it was the tragedy in Tucson or most recently our unified response to storms that have taken place in the South."
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U.S. forces killed bin Laden during a raid on a compound in Pakistan where he had been hiding, then buried him at sea.
Flag-waving crowds have been gathering at the lower Manhattan site of the attack since Obama announced bin Laden's death late Sunday.
Some local law enforcement agencies in the U.S. were adding security measures Monday, including at the site of the Sept. 11 attacks.
The Port Authority of New York and New Jersey said it will add more police at the facilities it runs, which include the airports, the George Washington Bridge and Ground Zero. The measures aren't a response to any current threat and all the facilities will operate normally otherwise, the Port Authority said.
"This response is not based on a current threat, but out of an abundance of caution until we have the chance to learn more," the agency said.
The Associated Press contributed to this report.