Boston & Roxbury Mill Dam

The Boston & Roxbury Mill Dam was an engineering project in Boston's Back Bay. Commissioned in 1814, the project intended to enclose the Back Bay basin and utilize flowing tidal waters for industrial production. Constructing the dam would allow water to reliably flow from the Charles River to the basin, creating an ideal environment for the era's industrial mills. The project additionally added a second route to the mainland that redirected traffic away from Boston's choked Orange Street causeway. Between 1818 and 1821, the dam was constructed by extending Beacon Street westward.

Dam data from Wikidata (CC0) plus curated additions. Summary from Wikipedia (CC BY-SA).