File:US Post Office, Rockford, Illinois 1951 postcard.jpg

Summary
This postcard image is in the public domain because it was published in the United States some time between 1933 (when the building was built according to the back of the card) and 1951 (when the card was postally used according to the back of the card) without a copyright notice. Postcards published in the US between 1923 and 1977 without a copyright notice are in the public domain. See https://www.webcitation.org/6h4M826Jr?url=http://www.ebay.com/itm/1951-Illinois-Postcard-Rockford-Post-Office-/371604596084?hash=item56855c2574:g:Lk0AAOSwgQ9V0iJ8 for an archived image of the back of the card showing postal use in 1951 and no copyright notice.
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