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Saturday, December 23, 2006

North Tower Topped Out, December 23, 1970

Today in 1970, the North Tower of the World Trade Center complex reached its full height: 1,368 feet. It and the South Tower were the tallest buildings in the world, if only for a short time. While the World Trade Center today evokes memories of September 11, 2001, the twin towers were a part of the New York City culture for a generation.

The idea that became the World Trade Center complex was first expressed in the 1950's as a way to breath new life into the Lower Manhattan area. Plans were made public in 1961. Architect Minoru Yamasaki was hired as the buildings' architect with Emery Roth & Sons serving as the associate architectural firm. Yamasaki's design called for two giant 110-story modernist structures. They would tower over the Empire State Building, the site that had, at one time, held the title of world's tallest building for nearly 30 years.

Groundbreaking for the project took place on August 5, 1966. The Port Authority of New York and New Jersey oversaw the construction of the buildings. To make room on the crowded island of Manhattan, thirteen square blocks of buildings were torn down. This area had been known as Radio Row because of the many electronics shops found there. Some of the low-rise buildings were built before the Civil War. Such was the cost of progress.

The World Trade Center towers presented some interesting engineering challenges. To overcome them, several innovative new technologies were employed. First, there was the issue of the buildings' foundations. Instead of the traditional foundation used for most buildings, the structural engineers assigned to the project designed what became known as the Bathtub. Put simply, the Bathtub was a giant concrete box in which all the buildings of the World Trade Center Complex were built. This solved the problem of river water from the nearby Hudson flooding the buildings' basements or putting undue pressure on traditional foundations. More than one million cubic yards of dirt and rock were excavated from the site to make room for the Bathtub. This fill was strategically dumped into the Hudson River and created 23 acres of dry land next to the World Trade Center site. Today, the area is know as Battery City Park.

The Twin Towers, like all skyscrapers, tended to sway and vibrate in high winds. Traditionally, tall buildings had been braced using load-bearing internal walls. The Towers used a new design that called for a strong central core. The core ran the full height of the building and contained stairs, elevators, wiring, ducts and pipes. Surrounding that were the floors and walls of the useable office space, which were attached to the core. The outside walls of the towers were made of light steel and concrete. Essentially, the central core supported the entire weight of the building, a design which allowed the rest of the building to be constructed of relatively lightweight materials. This kept construction costs down.

Another innovation was the use of sky lobbies; this idea was first used in Chicago's John Hancock Center. Sky lobbies are floors which are served directly from the ground floor lobby by express elevators. From the sky lobbies, commuters board local elevators which stop at each floor. The Twin Towers each had two sky lobbies located on the 44th and 78th floors. The use of sky lobbies allowed fewer elevator shafts to be built than otherwise would have been necessary. This meant more office space.

In addition to the towers, five smaller buildings completed the World Trade Center complex. The last was built in 1987. Underneath the 16-acre area was a large shopping mall and stops for the subway and Port Authority trains. By the time of the complex's dedication on April 4, 1973, more than $900 million had been spent. To the world, the Twin Towers came to symbolize New York City.

While the world may have been in awe of the structures, some New Yorkers were less than pleased. During the 1970's, a common joke among Manhattanites was that the towers were actually the boxes that the Empire State and Chrysler Buildings came in. Eventually, the complex became just another part of the skyline and became the home of the more than 500 companies, many of them financial firms with ties to Wall Street.

Today, the towers of the World Trade Center are just a memory. Part of the reason they were attacked was because they were so emblematic. The new World Trade Center, which is expected to be completed some time in the next decade, will include the Freedom Tower at 1,776 feet. The footprints of the Twin Towers will not be built upon and will become the site for the World Trade Center Memorial.

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