Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Pentagon Memorial, located just southwest of The Pentagon in Arlington County, Virginia, is a permanent outdoor memorial to the 184 people killed in the building and on American Airlines Flight 77 in the September 11, 2001 attacks (not counting the hijackers aboard the plane). Designed by Julie Beckman and Keith Kaseman of the architectural firm of Kaseman Beckman Advanced Strategies, the memorial opened to the public on September 11, 2008.