Indiana limestone has been a popular choice for public buildings since the late 19th century. Limestone quarried in Indiana was used for the initial Pentagon construction and also for the repair of the damaged southwest side of the Pentagon after the 9/11 attacks. To learn more about Indiana Limiestone and its usage on the exterior of the Pentagon, see the document below:

Indiana Limestone Document 

The two planes that terrorists intentionally crashed into the World Trade Center Twin Towers in NYC were wide-body (dual-isle) Boeing 767s, while the planes that terrorists intentionally piloted into the Pentagon and were trying to fly into the US Capitol (crashing instead in a field in Pennsylvania, thanks to the heroic actions of the United 93 passengers) were narrow-body (single-isle) Boeing 757s.  For more information about the characteristics of  these aircraft, see the document below:

Boeing 757 - 767 Comparison Document 

The Pentagon 9/11 Memorial Docents recognize the importance of the USS Arlington and value our ongoing working relationship with many members of the ship’s crew. The USS Arlington is an amphibious transport dock that is named after Arlington, Virginia, the location of the Pentagon, and also the crash site of American Airlines Flight 77 during 9/11 attacks, commemorating those who lost their lives during the attack along with First Responders who fought the fire, partnered in the rescue of the injured, and provided security as events at the Pentagon unfolded on 9/11 and after. There is also a Tribute Room onboard the ship that is described in considerable detail in the document below, along with general information about the ship. For more information, see the document below:

USS Arlington Document