Raised in the 1960s, the glass-and-steel towers were designed and built with innovation and special attention to safety and stability because of their extreme height. Engineers wanted to make sure the towers could withstand hurricane-force winds of up to 200 mph - on an especially windy day, the towers could sway up to several feet in either direction. With memories of a 1945 plane crash into the Empire State Building lurking in their minds, engineers and architects also designed the towers to withstand the force of a Boeing 707. There are several reasons to make the tower magnificent. Firstly, the engineers agreed that the secret to ensuring the buildings would stand tall under extreme circumstances rested in their supporting steel columns, which were set up differently from most skyscrapers'. Secondly, the majority of the beams framed the outside walls of the towers: 61 beams per 211-foot side provided maximum reinforcement.