In a May 1943 issue, LIFE noted that the exterior of the Pentagon "has a gray limestone facade, although more than half of the building's substance is sand and gravel dredged from the bottom of the Potomac River." / LIFE photo by Myron Davis
World War II means two things to U.S. military veterans of a certain age: the building of the Pentagon, and LIFE magazine (TIME's corporate sibling). Every week LIFE chronicled the war for millions of Americans.
LIFE.com has just released never-before published photographs of the Department of Defense headquarters building under construction. Dig those pneumatic tubes (altho' the SecDef's office looks familiar)! Not only does it remain the world's largest office building, but the federal government broke ground for it on September 11, 1941 - precisely 60 years before a hijacked airliner crashed into its western facade, killing 184, including 125 inside.