A U.S. Marine, one of one hundred eighty-four joint service troops, prepares to unveil the Pentagon Memorial on Sept. 11, 2008. The national memorial is the first to be dedicated to those killed at the Pentagon on Sept. 11, 2001. The site contains 184 inscribed memorial units honoring the 59 people aboard American Airlines Flight 77 and the 125 in the building who lost their lives that day.