• 171 Main Street, former Hall House, built 1796. According to the NRHP nomination "Originally, it was a conventional two-and-one-half-story, five-bay structure. A third floor added in the 1870s, storefronts installed in the 20th century..." Now part of Middlesex Plaza. (I suspect this building may be completely a replacement for Hall House, and may not integrate any of the old building.)
• 179 Main Street, former Middlesex Assurance Co., built 1867, now part of Middlesex Plaza
• 191-195 Main Street. At least part of this building dates from 1835, but according to the NRHP nomination "a brick fire wall down the center of the building, suggest[s] the possibility that originally it was one-half its present size... [B]y 1856 both halves were in place, but as a two and one-half story building with gable roof... The full third story was added c. 1891, along with a new front facade...
• 203 Main Street (corner of College Street), former Universalist Church, built 1839, later (from 1916, and with its appearancemuch altered) Odd Fellows hall, now a Thai restaurant.

All of these are contributing properties of the Metro South Historic District, which is on the National Register of Historic Places.

• 
  Similar view, different angle, circa 1980