The Neponset Bridge Corporation was to construct and maintain the road in Dorchester from the bridge to the “Dorchester Lower Road” (Adams Street at Victory Road). Since the bridge was considered an extension of the Quincy Turnpike, although officially separate, the road on the Dorchester side became known as Neponset Turnpike. The entry in the list of streets in Boston reads: Neponset Avenue, Dor.; from 358 Adams street to Neponset river, called Quincy turnpike on th plan dated 1844, and Neponset turnpike on plan dated 1856; laid out as a public highway or control assumed by County, December, 1858.
Sources:
Boston. Street Laying Out Department. A Record of the Streets, Alleys, Places, Etc., in the City of Boston. (1910), 331.
Frederic J. Woods. The Turnpikes of New England (1919), 103.