As the 20th anniversary of 9/11 approaches, television stations and websites plan a flurry of retrospectives and oral histories. Many will feature the original workers, engineers, and owners who built the World Trade Center. History.com released an article about the 10-year-long construction effort; some of the highlights include:
• The Twin Towers' chief architect, a little-known Japanese-American man born to a family of poor immigrants in Seattle, Washington, worked his way through architecture school by working fish canneries in Alaska. He won the job of designing the towers—at the time, the tallest buildings in the world. His biggest job to date: the 30-story Michigan Consolidated Gas tower in Detroit.
• Builders dug 70 feet into the bedrock and removed more than one million cubic yards of dirt to build the towers' foundation. Next, they dug a 3,500-foot-long, three-foot-wide trench around the perimeter and filled it with a slurry of water and absorbent clay to stop the foundation from filling with water. Later, they lowered enormous steel cages into the trenches and filled them with cement. They referred to their creation as "The Bathtub." History.com writes: "it was a tub that kept water out, and not in."
• The tower’s most significant innovation also played a substantial part in their collapse. The towers’ support pillars stood on the exterior of the tower rather than on the interior. External support meant a structural façade that supported the towers without blocking the building with columns or pillars. Unfortunately, terrorist plane attacks punctured the structural shell, crippling the towers' integrity.
• The builders used more than 200,000 tons of steel to build the towers; they hoisted resources up the massive height with an Australian-designed, self-contained crane, nicknamed the "kangaroo crane." These cranes used hydraulics to "jump" upward as the tower rose, keeping the crane perpetually on top.
Other channels and websites plan retrospectives and specials about the World Trade Center in the coming weeks. For more information about this article, visit History.com.