US marks 9/11 with somber tributes, new monument to victims

People attending the dedication stand around the 93-foot tall Tower of Voices on Sunday at the Flight 93 National Memorial in Shanksville, Pa., where the tower contains 40 wind chimes representing the 40 people that perished in the crash of Flight 93 in the terrorist attacks of Sept. 11, 2001. (AP Photo/Keith Srakocic, Pool, File)

NEW YORK — Americans are commemorating 9/11 with somber tributes, volunteer projects and a new monument to victims, after a year when two attacks demonstrated the enduring threat of terrorism in the nation’s biggest city.