Pentagon designed for records storage. (Up front: news, trends & analysis).

The Pentagon has served as the United States' military headquarters since the end of World War II, but the 6.6-million-square-foot structure was originally designed for document and records storage--and that may have saved lives when the structure was attacked September 11, 2001.

According to a recent analysis by the American Society of Civil Engineers, the use of reinforced structural steel and other elements engineered into the building, which was initially designed as a solidly built warehouse more than 60 years ago, paid off when a Boeing 757 plowed 310 feet into the Pentagon's west wing corridors at 530 miles per hour.

"We had limited localized damage to part of the structural frame; we had collapse only in that limited area" Paul F. Mlaker, technical director of the U.S. Army Corps of Engineers, told CNN. Although the attack killed 189 people, including 125 in the building, experts say the death toll might have been much higher if the collapse of floors and resulting fire damage had been more widespread.