While it is easy to think of the 1920s as a fairly unified fashion period, with its waistless dresses, cloche hats, and short hair styles, skirt lengths varied a lot during the decade. They started out fairly long, then became short around mid decade, and then became longer again. This photo is clearly from the twenties, but I wondered at what point in the fashion curve. Two women have skirts just below the knee and two have longer styles. Was fashion heading toward the short skirt or away from it?
What are the clues? I looked through the reference book Fashion of the Roaring Twenties by Ellie Laubner for ideas. That long ropey necklace worn by the woman on the far right is a more common accessory of the early 1920s; in fact, you can see them already in the previous decade. Uneven hems and bias cuts were also a feature of the earlier 1920s. Since the women on the right look older, and younger women are more likely to keep up with fashion (although not always), I’m going to guess this picture was taken as skirts were getting shorter.
There are two unusual dresses in the picture, both in the middle. The women center left seems to be a fashion rebel—her dress has a waistline somewhere near her natural waist. The woman to the right is wearing a transparent dress, perhaps chiffon, with a full slip underneath. Although it reveals nothing, to me it is a very racy look.
Since I found this in a Chicago thrift store, my best guess is that we are looking at the shore line of Lake Michigan.