As New Milford entered the 20th century, residents wanted important items from the town's history preserved and displayed. In 1906–1907, during the town's Bicentennial, Memorial Hall above the library hosted a "Loan Exhibition" of 488 objects belonging to townspeople, and concern grew that these items might be scattered and lost when the temporary exhibit ended. In 1915, prominent citizens organized the New Milford Historical Society, and the State granted a charter to Helen and Kate Boardman, direct descendants of Daniel Boardman, the first minister of New Milford. Their will left their Main Street home to the society, along with an endowment fund and many valuable antiques. In 1922, two years after the death of Kate Boardman, the last of her family, the Boardman house opened as a small museum with Flora Greer Stilson as the first curator. Over the next several years, the society acquired the Bank Building from the Elijah Boardman property and the Knapp House, willed to the society by Mary Clissold Knapp. After the Boardman Main Street property was disposed of, more space was needed for the growing collection, and in 1963 a three-story building designed by architect Edgar Williams was constructed to serve as an exhibition hall, meeting and office space, and a venue for events. Blending colonial and modern architecture, it featured four eight-foot, 12-over-12-pane windows, three overlooking the town Green, and a colonial front door that had once been the side Bank Street entry of the United States Hotel on the Green and had been part of a temporary exhibition of The Metropolitan Museum of Art before returning to New Milford. The main gallery was improved over the years, most significantly in 2016, when the windows were exposed, new flooring and lighting were added, and the walls were painted. The gallery displays antique furniture, original Ralph Earl paintings, New Milford Pottery, silver, Connecticut-made clocks, items belonging to founding families, and curiosities including the 1754 meetinghouse pulpit and a hitching post from the Green.