A memorial wreath sits in front of the North American Aerospace Defense Command and U.S. Northern Command memorial to those who died on Sept. 11, 2001, during a remembrance ceremony at Peterson Air Force Base, Colo., Sept. 11, 2017. The memorial is comprised of a steel girder salvaged from the fallen World Trade Center buildings in New York City, soil from the crash site of United Airlines Flight 93 in Shanksville, Pa., and a concrete and granite planter in the distinctive shape of the Pentagon. Air Force photo by Jhmol Bansil