John Templeman Coolidge was an artist and antiquarian and lover of the sea. The Wentworth mansion no doubt appealed to all his interests. Coolidge carefully restored the neglected house and grounds with advice from his friend, Sumner Appleton, founder of the Society for the Preservation of New England Antiquities.

Coolidge added a guest wing about 1920, replacing the former carriage house; however, he was careful to maintain the building's architectural integrity.

The house served as an active gathering place for the family (Coolidge had seven children) and friends, many of whom built residences nearby. Coolidge's first wife, Katharine, was the daughter of the historian Francis Parkman, who used a second floor bedroom as a summer writing retreat during his later years. After Katharine's death in 1900, Coolidge married Mary Abigail Parsons in 1913. The widow Mary Coolidge donated the property to the state of New Hampshire in 1954.