The entire district was laid out by architect Charles Bulfinch on land reclaimed from the old Mill Pond (also known as North Cove), and is now populated by well-preserved commercial buildings from the 1870s through early 1900s.

There is a particularly fine example of Second Empire architecture at 48–72 Canal Street, designed by Gridley J. F. Bryant and completed in 1871 for the Paine Furniture Company.

There are a number of good examples of the Beaux Arts style, including two on Portland Street designed by Stephen Codman.

A number of older buildings (dating to the mid-19th century) line part of Causeway Street, but have been compromised by removal of their upper floors and modernization of their facades.

[2] With the construction of the Charlestown High Bridge and aerial John F. Fitzgerald Expressway/Central Artery during the 1950s roughly the eastern 1/3rd of the Bullfinch Triangle was occupied by the expressway and its associated on/off ramps.