I call this series the Sunbonnets Seasons. Even though they are not sunbonnets, they are published by Ullman and Bernhardt Wall is the artist, just like all the sunbonnet series I have showcased thus far. Seasons series number 57 is copyrighted 1906, and 3/4 cards I have were sent that year as well.
The Summer girl, to the left, is building a sandcastle at the beach. Winter is going sledding, Spring is collecting flowers, and Autumn is picking apples. All the girls are wearing the big red hat and a pink dress.