In 1887 David Flint, a summer resident of Winter Harbor, made the decision to build a Unitarian chapel on land that he owned which lay adjacent to his large cottage on Inner Harbor. Flint was a Boston lumber dealer, who, after being widowed, had married his wife's doctor, a local woman named Almeda Guptill Baker. Being a staunch follower of William Ellery Channing and believing that there was sufficient interest in Unitarianism here, Flint felt that there was need for a meeting place.

In the winter of 1887-1888 both beach and field stones were brought to the site of the future chapel by people of the village since it was much easier to transport them over the frozen ground rather than wait for summer when the chapel was to be built. The chapel walls were begun on June 18, 1888, and the building was finished and ready for dedication ceremonies on August 28, 1888.

The auditorium window, at the west end of the building, contains a likeness of William Emery Channing, the founder of Unitarianism.

The vestry, which was originally known as the Channing Free Library, displays a likeness of David Flint. This window was donated and installed as a surprise gift to Mr. Flint. The double desk used by the librarian was originally used in Flint's lumber office on long Wharf in Boston in the middle of the 19th century. A record of the desk's history is pencilled in one of the center drawers.