While digging around at my folks house today, I came across an old Minneapolis Tribune Marketplace section from July 8, 1979, that was wrapped around an old gravy boat or some such thing. And on page 6D, I saw this picture with the following small article…
Washington Square takes shape
A new skyscraper continues to take shape in downtown Minneapolis, at Washington and Marquette Avs. The 22-story building, called Washington Square, is scheduled to be completed in August 1980. The structure, being built by Northwestern National Life Insurance Co., will offer office space for rent. Workmen are using an unusual process called “slip forming” on core walls to speed construction. In slip forming, a wooden platform about 20 feet high and built in the shape of the core walls is lifted continuosly while workmen pour concrete into the rising form. The platform is lifted at a rate of about six inches an hour, allowing time for the concrete to harden. Traditionally forms are filled with concrete, then removed and reconstructed floor by floor.
1979 Minneapolis Tribune photo scanned by me, current photo by Wikipedia