In 1994 the Society did the research and applied to the Maine State Preservation Commission to have two significant historic districts approved for National Register designation.

The first district runs up and down Calais Avenue and from Calais Avenue to Swan Street. It includes Domestic single dwellings, a Religious facility and Landscape Park with significant dates from 1805, 1850 and 1875. with two significant architects, Matthew Stead and J. C. Rockwood. Examples of Federal, Greek revival, Italianate and Queen Anne style buildings are present in this district.

A second district is called The Hinkley Hill Historic District. and extends from #305 to #326 Main Street and include 8 domestic private dwellings. Their architectural classification is Gothic, Italianate, and Greek revival. This district contains a significant proportion of the community’s most notable and well-preserved mid-nineteenth century residential architecture. Its earliest house dates from 1820, a Federal style one-and-a-half story cape. Between 1850 and 1855, a group of three Gothic Revival style houses were built on adjoining lots on the North side of Main Street. This is probably the most photographed spot in Calais and is worthy of its reputation.

The boundary of the Hinkley Hill District moves from the south side of Main street to the north side between houses 5 and 10 on the location map to make one contiguous district that includes all the significant houses.

Slides of these properties are available so that a slide presentation can be made of both historic districts.