On another forum I was asked a question about how Melnea Cass Boulevard came into existence. The illustration above, from the 1965/1975 General Plan for Boston and the regional core, shows the proposed connections between the Southwest Expressway and an inner belt highway. The inner belt highway (I-695) would have connected to I-93 to the east and Central Square and other points to the west before reconnecting to I-93 north of Boston. These highways were never built.
The plan would have required tunnelling under part of the Fens (one can see the MFA to the immediate right of the Fens, for a sense of position) before coming back above ground to bridge the Charles River. Landmarks to orient yourself include Chester Park on Mass Ave, which is the ellipsis in the upper center, and the Reggie Lewis Track Center was built in the vacant space in the bottom center along Tremont Street. What this rendering doesn't show is the scale of the interchange required to connect the Southwest Expressway to the inner belt highway.
You can read more about the Southwest Expressway, and see more photos and a rendering of the interchange, here. When the project ultimately came to a halt, the cleared area that would have dedicated to the inner belt became Melnea Cass Boulevard. From my own perspective, the location of Melnea Cass Boulevard, which tracks fairly closely the old Boston/Roxbury border, further strengthens my argument about the problem of "forgotten" areas. More Roxbury/Boston border information can be found here.
I also recommend Rites of Way: The Politics of Transportation in Boston and the U.S. City (1971) by Alan Lupo, Frank Colcord, and Edmund P. Fowler.
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