President Obama, Officials Attend 9/11 Memorial Museum Opening Ceremony

NEW YORK, NY - MAY 15: New Jersey Governor Chris Christie greets Port Authority Police Officer David Lim before the dedication ceremony at the National September 11 Memorial Museum May 15, 2014 in New York City. The museum spans seven stories, mostly underground, and contains artifacts from the attack on the World Trade Center Towers on September 11, 2001 that include the 80 ft high tridents, the so-called "Ground Zero Cross," the destroyed remains of Company 21's New York Fire Department Engine as well as smaller items such as letter that fell from a hijacked plane and posters of missing loved ones projected onto the wall of the museum. The museum will open to the public on May 21. (Photo by John Munson-Pool/Getty Images)