A man with strong academic art training, Harry Hoffman was judged by his peers to have done best with his landscapes when he painted what he saw and set aside the theories. He studied in Paris, worked at Yale University with John Ferguson Weir, and was a student at the Art Students League with Frank DuMond. Willard Metcalf had by far the strongest influence on Hoffman, encouraging the young artist to paint in the style of impressionism.
In 1902, Hoffman went to Old Lyme, Connecticut, and stayed at the Florence Griswold House, returning for many subsequent summers. At one point, when he was exceptionally low on money, he nearly became a professional baseball player, but was dissuaded by his painter friends.
He married Beatrice Pope from East Orange, New Jersey, who was also staying at the Griswold House, and they lived in Old Lyme. In the 1920s, he had a reputation for his underwater life paintings, having made a bucket with a glass bottom that he floated on the water for special vantage points. Intrigued by the many colors he found in the ocean, he accompanied the naturalist William Beebe on research trips to the Galapagos Islands, Bermuda, and British Guiana.
In 1930, Hoffman was elected an Associate of the National Academy of Design. He was also very helpful to Florence Griswold in her old age when she was about to lose her house. Successfully avoiding that loss, he served as the treasurer and fundraiser of monies to save the building as a home during her lifetime and as a museum when she died.
Hoffman lived to be ninety-two years old, the longest lived of the Old Lyme painters.