Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:Isabella_Furnaces_1905.jpg
This is a scan from Pittsburgh's Landmark Architecture (ISBN0-916670-18-X) of a photograph from the Photographic library and collections of the Pittsburgh History & Landmarks Foundation. The author of the photo is unknown but dated "around 1905" (pp 11) and so presumed public domain.
Captions
Isabella Furnaces (Pittsburgh, Pennsylvania) in 1905