Senior Pictures, Probably St. Peter, MN

These are photos I found at an antique store in Minnesota. Ruth wrote on the back of her photo St. Peter, Minnesota. The photos were taken by a photographer in Mankato, MN. The girls are Marg. , Marjori, Ruth, and Orda. Ruth was the only one whose last name was included, it was Hanson. I'm guessing, by the hair styles, these were taken in the 1920's  but I suppose it could be the 1930's also.