years. Both towers are the result of collaboration between architect Bruce Graham and engineer Fazlur Rahman Khan. Khan invented a tubular framing system that made it possible to build higher than ever before. This system has been adapted and is still used today for some of the world's most recent tallest buildings, including the 828-meter-tall Burj Khalifa, designed by SOM and completed in 2010.

In the 1960s and 1970s,