Bisected by Washington Street, the twin squares of Blackstone and Franklin originated in the plan for a single large oval park proposed by Charles Bulfinch in 1801. The gradual departure from the Bulfinch scheme can be seen in an 1814 map of the city that shows two halves of an oval park enclosed within the grid pattern of the streets. Development of what came to be known as the South End proceeded very slowly until the 1850s, as this area was still well beyond the city center. By that time the bisected oval park had become two squares. Row houses were built facing the squares, the most outstanding survivor being the block developed by Frank W. R. Emery in 1853 on Blackstone Square. Charles F. Parker's design for this brownstone row owes its stylistic inspiration more to New York than Boston, with exteriors consisting of a conservative Italian Renaissance classicism with pilasters, entablatures, and pediments.

Dominating Franklin Square is the Franklin Square House retirement home. M. M. Ballou, publisher of Ballou's Pictorial, erected this building as the St. James Hotel. John R. Hall's design for the mansard roofed structure evokes a grandeur comparable to the great hotels of New York City. With four hundred rooms, the building included a steam-powered elevator and claimed among its visitors President Ulysses S. Grant. By 1882, however, the New England Conservatory of Music (see
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) had purchased the building. When the music school moved to the Fenway in 1902, the property became the Franklin Square House for Women and a large addition was made on the north side.