Boston’s John Hancock Tower was still under construction when winds of 75 miles per hour struck on January 20, 1973. By morning, 65 exterior glass panels—each weighing 500 pounds—lay shattered on the ground. Around that same time, construction workers reported severe swaying of the structure during winds. Were the two phenomena linked or was the timing coincidental? Discover how tuned-mass damper technology became an effective tool for controlling wind-induced (and earthquake-induced) sway—and why all 10,344 windows had to be replaced.