The Pentagon is completed after sixteen months of construction

On January 15, 1943, construction of the Pentagon was completed, approximately sixteen months after work began in September 1941. The project cost approximately $83 million and produced one of the world's largest office buildings, containing roughly 6.5 million square feet of floor space. Its distinctive design incorporated five sides, five above-ground floors, two basement levels, five concentric corridors on each floor, and a central courtyard occupying approximately five acres. Each exterior side measured about 921 feet, while the building reached a height of approximately 77 feet. Construction had proceeded section by section, enabling completed portions to be occupied before the remaining work was finished. The building's completion provided the War Department with a centralized administrative headquarters during World War II and established an architectural landmark that would remain closely associated with American military leadership.