It is a tidal bay, and at low tide primarily tidal flats. Native American fish weirs in this area, off of what is now the Common, go back at least 1000 years. The dam is the brainchild of Uriah Cotting and the Roxbury Mill Corporation. The structure is 50 feet wide and one half mile long with a toll road running over it between a row of trees. It is called Western Avenue and later Beacon Street.
Back Bay is annexed to Boston.
It is the idea of horticulturist Horace Gray. The Garden is later redesigned by George Meacham in 1859. A second perpendicular dam is extended from Mill Dam to Gravelley Point, Roxbury that divides the bay into two parts. The Boston and Worcester and Boston and Providence Railroads run across the marsh. Steam power and railroads combine to accelerate the filling of Back Bay.