Past the Bullfinch era, Boston's two grand periods of growth coincided with Richardson's new works (Trinity Church onwards) and the emergence of MIT Modernism (Gropius, Rudolph, Sert, Pei, etc.) who gave Boston's downtown arguably the greatest collection of Brutalist works in a single city north of Brasilia. City Hall aside, the best from the latest of these eras seems to be accepted as part of Boston's fabric. Not sure how stodgy the place is when Cambridge is the location of the only work by Corb in North America.
As, arguably, the last interesting architectural development in the USA was the preservation movement, couldn't one argue that here, too, Boston was at the forefront? They have certainly ducked out the worst of the PoMo and Starchitect horrors that litter every other downtown down south.