NEW YORK – The redevelopment of what once was Ground Zero passed another milestone Thursday when President Obama helped dedicate the National September 11 Museum in the cavernous foundation hole of the office complex destroyed by the 2001 terror attacks.
"To all those who responded with so much courage ... it is an honor for us to join in your memories, to recall and reflect but above all to reaffirm the true spirit of 9/11: love, compassion, sacrifice and to enshrine it in the heart of our nation forever," Obama said, addresssing the "families of the fallen." "All who come here will find it to be a profound and moving experience."
Earlier, the president and first lady toured the memorial with former New York Mayor Michael Bloomberg.
Attending the dedication at the museum in Lower Manhattan were hundreds of survivors, family dembers of victims, first responders and recovery workers.
Obama introduced Alison Crowther, the mother of Welles Crowther, who died on Sept. 11 wearing a red bandanna while helping evacuate fellow workers in the South Tower of the World Trade Center. The president also introduced Ling Young, one of the workers Crowther saved.
"For us he lives on in the memory of the people he helped," his mother said. "Welles believed we are all connected as one human family . ... This is life's most precious meaning. It is our greatest hope that when people come here and see Welles' red bandanna, they will remember how people helped each other that day, and we hope they will be inspired to do the same in ways both big and small. This is the true legacy of September 11."
Bloomberg said the museum will take its place in American history along with Pearl Harbor and the battlefield at Gettysburg. The museum, Bloomberg said, is a "reminder that freedom carries heavy responsibilities."
"Walking through this museum can be difficult at times but it is impossible to leave without feeling inspired," Bloomberg said.
The museum's opening is the latest sign of change at the site of the World Trade Center. The 9/11 Memorial opened on the 10th anniversary of the attacks, and last year One World Trade Center reached its signature height of 1,776 feet to become the nation's tallest building. The office tower is expected to open later this year.
MORE: September 11 museum at a glance
The museum attempts to both tell the story of the 9/11 attacks and remember their nearly 3,000 victims.
It does so with audio, including a fire chief's report from the South Tower shortly before it collapsed; video, including some of the hijackers' easy passage through airport security; photos, including facial portraits of every victim; and an array of artifacts.
The latter include pieces as large as the columns that supported the center's twin towers and as small as a $2 bill from a victim's wallet that matched one he'd given his wife to symbolize their second chance at love.
The museum was built around a series of huge objects and structures, including an exterior staircase that led evacuees to safety; the last steel column to be hauled from the site; the 60-foot high retaining wall that held back the Hudson River even after the towers collapsed; and a cross-section of I-beams resembling a Christian cross that fell from the North Tower.
Visitors move through a glass and steel entrance pavilion off the memorial's plaza before beginning a seven-story descent to the exhibitions at bedrock level.
The museum was supposed to have opened on the attacks' 11th anniversary, but work was slowed and for a time halted by soaring costs, weak fundraising and jurisdictional disputes. Some relatives of 9/11 victims also have objected to various museum decisions, including one to move still-unidentified human remains from the Medical Examiner's office to a repository behind a wall at the museum.
Other controversies have included:
• Whether the museum's historical exhibit, by displaying the hijackers' photographs and names, glorifies them and insults their victims' memory.
• Whether a brief explanatory film about the 9/11 conspiracy unfairly links al-Qaeda terrorism with Islam.
• Whether the $24 general admission fee is too much.
After Thursday's dedication, the museum will be open around the clock for six days for free visits by 9/11 survivors, victims' relatives, first responders, recovery workers and Lower Manhattan residents. It opens to the general public May 21, although reservations for that day are sold out.