Forty-two years ago this week, on a cool, breezy day on the western edge of downtown Chicago, engineers placed the final steel girder into the sky, topping out the Sears Tower and officially making it the tallest building in the world. It would be another three months before the building, designed by Fazlur R. Khan, would reach its working capacity of 15,000 people.

Since its opening, the building has not only housed Sears, Roebuck & Company, but many other businesses as well, from fine-dining restaurants to prestigious law firms. In 1996, the Petronas Towers in Kuala Lampur, Malaysia, ended the Sears Tower’s 25-year reign as the tallest building in the world.

In 2009, the building was renamed the Willis Tower after a large portion of it was purchased by the Willis Group. Today, the Willis Tower is the second-tallest building in the United States after the recently completed One World Trade Center building in New York City.

Learn more:
Wonders of the World – PBS.org
Dr. Fazlur R. Khan