Charlestown Mortgage is located in the historic Charlestown Savings Bank Building in the Thompson Square area of Charlestown where Austin Street meets Main Street.

One Thompson Square was constructed in 1875, just after Charlestown ceased to be a city and became part of the City of Boston. It is a five story, 30,000 square foot structure, designed in what is known as High Victorian Gothic Style, a very popular style at the time, with beautiful multi-colored stonework on its front.

The owner/developer was the Charlestown 5 Cent Savings Bank, which started in 1854 in today's City Square but decided to build and move here. For your information, the successors of this original bank are now part of today's Citizens Bank. When the Savings Bank opened its doors at One Thompson Square in the mid-1870s, it only had offices on the 2nd floor. Next door, the gas company occupied the second floor space, and there were three stores on the ground or first floor. Over time, the bank took over the first floor by adding a banking floor and stayed here until the 1970s. Even today, the building is peppered with bank safes, reflecting its former uses.

In the mid-1870s at the original planning stage, the Bank convinced the Masonic Lodge to join with them to create a truly impressive five story building in Thompson Square. The building would have only been two stories without the Masons, who occupied the top three floors, with a banquet hall on the top floor accommodating more than 500 people; small meeting rooms along the front on the 3rd and 4th floors, and the large two-story Assembly Hall on the third with a capacity of almost 400 people. The Masonic Hall was in use until the late 1970s, when its functions moved. The Charlestown Savings Bank branch moved out at the same time to the Bunker Hill Mall.