Statistics for occurrence #1 of “Mason Street” in chapter 4 of Lucius R. Paige, History of Cambridge, Massachusetts, 1630-1877, with a genealogical register:

...ater StreetDunster Street. Crooked StreetHolyoke Street. Besides these principal streets were sundry highways. The highway to Watertown extended from Brattle Square through Brattle Street to Mason Street ; and thence was identical with the Path from Charlestown to Watertown. From this highway three others diverged southerly: one, to the ox-marsh, passing near the site of the Brattle Mansion-house; ...
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