MANHATTAN - The National September 11 Memorial Museum was formally dedicated today in a ceremony featuring survivors, victims' families and current and former mayors, governors and presidents.

President Barack Obama spoke at the dedication and said the museum tells the story of Sept. 11 so that future generations will never forget. The museum contains artifacts, pictures and stories of the thousands of people who survived or were killed in the attacks.

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The president also recognized the men and women who helped save lives in the attack, including those who gave their lives in the effort. He told the story of Upper Nyack man Welles Crowther, an equities trader and volunteer firefighter who helped rescue countless people from the South Tower until he was killed when it collapsed. Crowther was only known as "the man in the red bandana" until he was identified and the red bandana is now housed at the museum.

One of the people Crowther rescued, Lyn Young, also attended the ceremony, where she thanked Crowther's parents on his behalf.

"What this museum does is allow us to see that we absolutely can affect each others' lives by what we do at a time of crisis, how we are strengthened by what was done that day," said former New York City Mayor Rudy Giuliani.

Broadway singer LaChanze sang "Amazing Grace" at the ceremony. The Mount Vernon woman lost her husband on Sept. 11 while she was eight months pregnant.

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AP wire services contributed to this report.

To see extended video of the dedication ceremony in New York City, watch the clip to the left or go to News 12 Extra on Optimum TV channel 612.