It’s the Hotel 71 now. At the time it was starkly modern, a sleek steel assertion of the new world inserted into the old stone streets of Chicago. After a few years everything looked like the Executive House, and no one paid it any attention.
A Google Streets view can be had here. Go full screen, and compare it to its neighbor. It's interesting to note how the pictures of International Style buildings always show transparent buildings whose floors seem to float in the sky.
They never looked like that.