Bill Pool, a volunteer with the Air Mobility Command museum listens intently during the dedication ceremony of a memorial to those killed on Sept. 11, 2001, at the AMC museum at Dover Air Force Base, Del. on Sept. 11, 2013. The memorial, which incorporates two pieces of steel from World Trade Center tower one, a rock from the United Airlines Flight 93 crash site and a block from the damaged portion of the Pentagon, makes Delaware the 50th and final state to have a public memorial. The steel was acquired through the Port Authority of New York and New Jersey World Trade Center steel program. (U.S. Air Force photo/Greg L. Davis)