Who designed the US Pentagon and why did they choose its shape?

the pentagon was designed to enable the united states govt. to entrap and control a being from another dimension, which they thought they could control to help dominate world military affairs to US advantage. It worked for a while but what they have trapped inside the containment field which is the "pentagon" shaped building is no longer 'playing the game'. Thats what you get when you play with Yog Soggoths...

F.D.R. was the person who decided on the shape of the Pentagon. He wanted a design that was unique and stood out. (3 years working at the pentagon got me that answer :o)

Designed? I'm not sure it is any ONE person. I found this article from the US Army Corps of Engineers:

Brigadier General Brehon B. Somervell, an aggressive Engineer officer who headed the construction division, had another idea. On Thursday, 17 July 1941, he summoned two of his subordinates, Lieutenant Colonel Hugh J. Casey, also an Engineer officer, and George E. Bergstrom, a prominent civilian architect, and told them that by Monday morning he wanted basic plans and an architectural perspective for an air-conditioned office building to house 40,000 workers in four million square feet of space, not more than four stories high, with no elevators (later adjusted). Indeed, Lieutenant Colonel Casey and his staff completed the basic layout of a five-sided building by that following Monday, after what he later described was “a very busy weekend.”

http://www.hq.usace.army.mil/history/vignettes/vignette_34.htm

According to wiki:

Its unusual shape results from the fact that its originally intended site, Arlington Farms, fronted on Arlington Ridge Road and the Arlington Memorial Bridge approach, which intersected at an angle of approximately 108 degrees (the angle of a regular pentagon).[3] President Franklin D. Roosevelt had it constructed at its current location because he didn't want the new building to obstruct the view of Washington, D.C. from Arlington Cemetery.

And from the Defense Technical Information Centre

The Pentagon—a building, institution, and symbol—was conceived at the request of Brigadier General Brehon B. Sommervell, Chief of the Construction Division of the Office of the Quartermaster General, on a weekend in mid-July 1941. The purpose was to provide a temporary solution to the War Department’s critical shortage of space. The rapidly expanding War Department envisioned a single structure in which to house all its components, as opposed to constructing multiple temporary structures as was then the practice. Congress, cautious about the size of the expenditure and the enormity of the project, but anxious about events in Europe and the Far East that could require U.S. military intervention, appropriated the funds necessary to construct the War Department’s new home (approximately $83 million) on August 14, 1941. The groundbreaking ceremony took place on September 11, 1941.

The original site chosen for the Pentagon was a tract of land known as Arlington Farms. The site was bordered by five roadways thus dictating the concept of a pentagonal shaped building. Fearing the enormous building would interfere with the view of Washington, D.C. from Arlington Cemetery, President Franklin Delano Roosevelt directed the building be moved three quarters of a mile down river. The new location chosen was at the site of the old Hoover Airport, a brick factory, a pickle factory, a race track, and a low-income residential area known as Hell’s Bottom. On this site, the final design concept of an open air court surrounded by five concentric pentagonal rings (or corridors) traversed by ten spoke-like corridors was constructed.

The architectural style of the Pentagon is Stripped Neo-Classical. The building was constructed out of reinforced concrete made from 380,000 tons of sand dredged from the Potomac River and supported by 41,492 concrete piles. The designers’ ingenuity not only created a building that reflected the architectural style of the nation’s Capitol but also saved enough steel to build one battleship. At the height of construction, over 1,000 architects worked in an adjacent hanger producing enough prints to supply the 14,000 construction workers and tradesmen. Three shifts worked 24 hours a day, every day, constructing the Pentagon wedge by wedge. These wedges were occupied as they came on-line. The building was dedicated on January 15, 1943, nearly 16 months to the day after the groundbreaking.

The Pentagon sits on 34 acres of land including the five acre center court, making a footprint large enough to accommodate five Capitol buildings. The Pentagon has 6,500,000 gross square feet of space, 7,754 windows, and 17 1/2 miles of corridor. In spite of the building’s tremendous size, it takes only seven minutes to walk between any two points of the building because of its unique design.

http://www.dtic.mil/ref/html/Welcome/general.html