Re: Discarded sign...
That area is referred to as “Yard 7” in the B&M Somerville/Cambridge yards.
Inbound/outbound LCL and freight house, and (?)apparently where some meat reefers were transloaded.
The elevated structure at right is the MBTA “Green” line – WAY behind it is where the (current day) Museum of Science is located.
If you look at a current map, it is North/East of MA Rt 28 (Charles River Dam Rd.) and North/West of the Gilmore Bridge