This image was acquired from
flickr. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
sanitary ship canal excavation illinois chicago drainage sanitary ship canal sanitaryshipcanal blackandwhite monochrome black and white Glaciated bedrock. Found while digging the Sanitary and Ship canal in Chicago circa . Original size and material inch glass negative Digital Identifier GEO Part of the Illinois Urban Landscapes