This picture best reflects the hat style that says 1940s. Wonder if this was a Chicago hat, or taken in a remote part of Chicago, or a park, tho the hilly terrain does not look like Chicago. The picture was among those for sale at Antique and Resale on Harlem in Chicago, so it qualifies to be part of Chicago Millinery History. Maybe this is carrying it a bit too far, but it is a wonderful photo, none the less.
Happy 100th day of 2011!