The three long buildings were (probably) a rolling mill that are now the site of the the east end of Veterans's Memorial Bridge. Turn the plan about 90 degrees clockwise for a more geographically correct orientation. Where Commercial Street and Danforth Street come together on the plan are now Cassidy Point Drive. Where the Portland and Ogdensburg ran on a causeway just north of the mill buildings (in 1873), about three hundred yards of it is now the Fore River Pkwy Trail (due south of the hospital buildings).
What the #*** did we just hit, Over ???