Located at the Braintree Green, the Old Thayer Public Library is one of the older remaining institutional buildings in the town. The building is a result of the generosity of General Sylvanus Thayer (1785-1872), a Braintree native and retired officer of the Army Engineers. He donated $10,000 and gave an additional $10,000 for the support of the institution, oh and he also donated money for the Thayer Academy in Braintree and to Dartmouth College for the Thayer School of Engineering. Before he could see his gifts completed, he died, but his family made sure that the gifts were overseen accordingly.
The Old Thayer Public Library was designed by Hammatt and Joseph Billings, under-appreciated brothers and architects who designed some of the best buildings in the region. The one–story (yes it was a high ceiling) building has a slate hipped roof and two chimneys. The brick masonry walls rise from a continuous, finished granite belt above the granite foundation. Corners are quoined, and the deep eaves and molded cornices are supported by granite consoles rising from a continuous narrow granite stringcourse. The building was eventually outgrown as the population in the suburban city boomed in the 20th-century. It operated as a library until 1953, when it was replaced by a larger building across the street, replaced again in the 1990s by the current library.