There used to be a website called Civilwaralbum.com that had photos and maps of the Vicksburg Campaign and other sites of interest. There were two foundries in Vicksburg during the war Reading and the other was Paxton.
Civilwaralbum had a photograph of an iron door frame on South St, and said it was the only remaining structure from one of the foundries...can't remember which one....
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The civilwaralbum site no longer exists but parts of the site are apparently archived at the Library of Congress....
https://webarchive.loc.gov/all/20190104052030/http://www.civilwaralbum.com/vicksburg/index.htm