Fashion during the 1930's was cut with diagonal bias seams to be smooth and slinky. The back view of a dress was often its best feature. These illustrations are from an old scrap book of mine, so I can't give you the exact dates, however most are from the early half of this decade. These fashion illustrations are just a peek into the wide range of back views seen during that time.
If you are dating a vintage dress that seems to be from this era, check out the back, that may help determine what decade it is from even more than the front view. And if you are going to sew for summer, why not consider adding some back interest to your project, that could make it something special.