Re: South Boston Seaport
A bit off topic -- here is some on the Altantic Ave El -- when there were rails on the waterfront:
from the wikipedia " -- an all-elevated line which would run along Atlantic Ave. At the time Atlantic Ave was the heart of the fishing and maritime industries in Boston and home to ferry terminals. Both the Washington St Subway and Atlantic Ave El would service trains from the Main Line El (the elevated section of the old Orange Line, now demolished).
When the Atlantic Avenue El first opened, shortly after the Main Line in 1901, the Main Line went through the Tremont Street Subway , changing between elevated and subway at the Pleasant Street Incline and the Causeway Street Incline. The low level trolley platforms were altered with temporary high-level platforms to allow for elevated trains to unload passengers. Where the original Washington Street Elevated (the south part of the Main Line) turned west from Washington Street onto Castle Street (now Herald Street), it had a full three-way junction (Tower D) with the Atlantic Avenue El, which began by heading east between Motte Street (also part of Herald Street) and the New Haven Railroad tracks."
so it was a branch of today's Ornge LIne
continuing -- "The El turned north after a block onto Harrison Avenue, continuing to Beach Street, where it turned east for its first station, Beach Street, on the block just east of Harrison Street. The El turned north on Atlantic Avenue, with its second station, South Station, located just north of East Street, with transfers to the South Station intercity and commuter terminal, and, beginning in 1916, to the Cambridge-Dorchester Tunnel (now the Red Line). Next was Rowes Wharf at Broad Street and High Street, with a transfer to the Boston, Revere Beach and Lynn Railroad via a ferry from Rowe's Wharf to East Boston.
Continuing along Atlantic Avenue, the next station, at State Street, was named State Street and had, beginning in 1904, a transfer to the East Boston Tunnel (now the Blue Line). After merging with Commercial Street, Battery Street Station, just north of Battery Street, provided access to Boston's North End. Just south of Battery Street, on the east side, was the Boston Elevated Railway's Lincoln Wharf Power Station. At Keany Square, the Atlantic Avenue Elevated ended at the Charlestown Elevated, the north part of the Main Line, at a full three-way junction (Tower C), with the Charlestown El heading west on Causeway Street and north over the Charlestown Bridge.' --
http://en.wikipedia.org/wiki/Atlantic_Avenue_Elevated
So it provided a link from Downtown to South Station and back to North Station connecting to what became the Blue Line in the middle
But the Mollases Flood of 1919 was the begining of its end - and the last of it was taken down in 1942 to provide scrap steel for WWII
So the full line only existed for 20 years and it stopped entirely less than 40 years after it opened
Unfortunate as it woould be useful today especially since an elevated line could easibly continue on to the Innovation / Seaport distriict and beyond