"BosWash" was the term E.F. Schumacher used for the east-coast conurbanation, in 1973. Boston-New York-Philadelphia-Baltimore-Washington. In Small is Beautiful: <https://en.wikipedia.org/wiki/Small_Is_Beautiful>

It's sprawled more since.

Apparently the term was coined by Herman Kahn in 1967: <https://en.wikipedia.org/wiki/BosWash>