The WTC, conceived in 1962, took off in 1964 when a mostly unknown American-Japanese architect called Minoru Yamasaki won the commission for building the World Trade Center. He, and Emery Roth as joint architect, developed several models of smaller scaled towers, before the final visionary design solution of the two towers, that satisfied the Port Authority’s office space requirements of 10 million square feet, was agreed upon.


The building with its own zip code.
Following the city within the city concept, pioneered at Rockefeller Center, the World Trade Center, was the world’s largest commercial project occupying a 15-acre area, bounded by Vesey Street on the north, Church street on the east, and Liberty street and West Street on the south and west respectively. Designed harmoniously, around an urban open space, WTC1 and WTC2 - widely known as the Twin Towers, and five other smaller low rise plaza buildings developed virtually into a city, self sufficient with its own police and medical facilities. WTC3, the Marriott Marquis Hotel (also known as Vista International Hotel) with 22 floors, was completed in 1971 by Skidmore, Owings and Merrill. WTC4 also known as the South Plaza Building housed the Commodities Exchange with 9 floors. WTC5 or the North Plaza Building had 9 floors. WTC6, with 8 floors, was the Customs House handling the customs and collection activities for the NY-NJ Port Authority was completed in 1973 and replaced the old Customs House at Bowling Green. WTC7 with 47 stories was the latest addition in the complex, included the Mayoral Emergency Command Center and was completed in 1987 by Emery Roth & Sons. Lastly but not the least were the seven levels of immense underground facilities including a shopping mall, parking facilities for some 2,000 cars, subway lines and stations and machinery for the maintenance of the towers. (Aerial photo by spaceimaging.com. Copyright ©Space Imaging. All rights reserved. Online and news media distribution or publishing requires permission from Space Imaging.)

The construction started in 1966 with consulting engineers Leslie Robertson, as the structural engineer; John Skilling, Frank Lombardi and Jack Kyle as the chief engineers of the Port Authority. The construction of the colossal WTC cost more than a billion dollars and was officially dedicated in April 1973 even though life in the towers had begun as early as 1971 when banks, brokerage houses, insurance companies and law firms moved into the buildings.


"A living representation of the faith of man in humanity", Minoru Yamasaki
The towers were built on six acres of landfill. Nearly 1.2 million cubic yards of earth and rock were removed from the excavation and were used for landfill for the nearby Battery Park City.The foundation of each tower had to extend more than 70 feet below ground level to rest on solid bedrock. The North (WTC1) and South Towers (WTC2) were 208 feet wide and rose up to 1368 and 1362 feet respectively with the North Tower topped with an additional 350 ton antenna, adding 330 feet to its total height. Each tower weighed approximately 500,000 tons, had 110 floors and more than 43,000 windows each 22 inches wide (Yamasaki was known to feel uncomfortable at great heights), giving a total glass façade of 215,000 square feet and made the towers appear from afar to have had no windows at all.

Three columns were joined together to make the external prefabricated pattern. These closely spaced steel columns, finished with a silver-colored aluminum alloy, were 18 3/4" wide and set only 22" apart, and formed a prefabricated steel cage that housed the central reinforced steel core which in turn housed the high speed elevator shafts. These were designed not to transfer stress to the core of the tower from winds and earthquakes. The inner tube or core and the external tube of columns were connected with floor trusses spanning across the two tubes. The job of the steel trusses was twofold; one to support the concrete floor slabs and secondly to tie the external column cage to the inner core thereby preventing the columns from buckling. That resulted into an acre of rentable space per floor since there were no other columns between the core and the façade, making the towers resistant and light with probably 50% less steel than a conventional structure but as strong (about 200,00 tons of structural steel were used in the construction of the WTC). Each tower had an allowable sway margin of approximately three feet from true center in strong wind storms.

This simple yet elegant, innovative structural design integrated extremely well with the architectural design and business goals generated a column free interior space, ideal for working environments and made for highly sought after office space, fulfilling the ambitious plan of Nelson and Dave Rockefeller.

The towers were broken at 1/3 and 2/3 of the height as they were divided into 3 sections with a system of local and express elevators. Passengers were changing at “sky lobbies” on 44th and 78th for local elevators to get to their respective floors. There were 104 elevators in total per tower. The single express elevators that went all the way to the top rising at 1,600 feet per minute were used to access the observation deck on the South Tower opened in December 1975 and the “Windows on the World” restaurant on the North Tower, opened in April 1976. The 10 stories high, vast lobbies accommodated the constant human flow during business hours since more than 130,000 people flowed through the complex daily.

At the time of their completion in 1973, the World Trade Center Towers, grabbed the honor of being the tallest buildings in the world. Two years later, the Sears Tower in Chicago seized the position, but the World Trade Center towers still dominated the Manhattan skyline and minds of the people and stood out as the first image associated with New York itself.

The very same engineering model that made possible the building was what caused it to fall. Earlier skyscrapers had columns spaced evenly across every floor. The World Trade Center had columns only in the perimeter of the central core, that contained the elevator shafts, and load bearing columns along the exterior walls. The whole complex was destroyed by the collapse of the Twin Towers. Amazingly “The Sphere”, a bronze spherical sculpture that was the focal point of the urban open plaza of the 5 acres, originally created in 1971 by artist Fritz Koenig, and which had been dedicated as a monument to world peace through international trade, it was only partially crushed by falling debris and now resides in Battery Park where it stands as a reminder of the tragedy.


September 11, 2001.
In the first attack on February 26, 1993, the terrorists hadn’t been able to penetrate the towers and the explosion in the underground garage of One World Trade Center almost bounced back creating a 22-foot-wide, five-story-deep crater. But the elevator shafts had acted like huge chimneys sucking up the smoke from the blast and sending it up, resulting in six people being killed and more than a thousand injured. WTC was forced to close for several weeks disrupting the operation of hundreds of businesses. Even the hit by the planes on September 11 traveling at hundreds of miles an hour might have not succeeded, but for the weakness in the connections between the floors and the columns.

Trusses had been designed for the safe loads expected and more, but under the intense heat of the estimated 10,000 gallons of burring jet fuel with temperatures that may have reached 2,000°F, the trusses failed causing the floors that actually kept the columns together to detach from the core and the outer walls. The resultant fires weakened the infrastructure of the building, collapsing the upper floors and creating too much load for the lower floors to bear as the upper floors pancaked down onto the lower floors, causing a domino effect that left each building in ruins within seconds. In fact, eleven seconds were enough for the WTC2 to collapse. The south tower collapsed at 10:05 am and the north at 10:29.am. In a few minutes the whole area was a pile of smoking rubble, hundreds of feet high. WTC7 was also heavily damaged from falling debris and collapsed later that day.


The design of the WTC had been a heavily debated project during its construction in the 60s. According to the critics, the view points ranged from admiration of the clean and simple design to the purposeless gigantism and shattering of the urban scale and the Manhattan skyline. However, in the eyes of the New Yorkers, the towers stood as a symbol of the city and the aspirations of man himself. It was the building that everybody wanted to work on. It was a symbol of the power of the American capitalism, the hallmark of the Manhattan skyline for more than 30 years, the headquarters of the financial institutions for New York and the nerve center of the world’s economy and as Yamasaki said “… A living symbol of man’s dedication to world peace …”