I had both of those dresses (or ones remarkably like them) in my wardrobe during high school and college. Those figures were created by "boned and wired" torture garments called "long line bras".
There's a movie filming in Austin now that is set in the 1950s. I went to to a costume fitting last week and was surprised that the warehouse full of vintage clothing didn't include many of the stiff undergarments necessary to shape us for a correct fit. Back then they didn't shape clothes to fit women, they shaped women to fit the fashions.