The Main Street Historic District is located on the district's namesake from Portland Street to roughly Swans Falls Road. The district is a narrow elongated rectangular area located down the town's principal street and is approximately fifty-five acres in size. It consists of mostly residential buildings, but does include three commercial properties, a religious building, a park, and a private academy. There are thirty-five contributing buildings (with nine properties dating before statehood) and five non-contributing buildings.

Located on a ridge between the Back River and Sasanoa River, the Heal Family House faces former agricultural fields and Robinhood Cove. The house is a good example of Federal-style architecture and it stands two-stories tall with a large central brick chimney. Its windows and doors are symmetrically placed along the front facade. The central entry has a wood paneled door that is accented with pilasters, a four-pane transom, and a projecting cornice. The house has a side ell with another entry that has a classical door surround.

Set back on a hill overlooking University of Southern Maine (USM) Gorham campus, the Academy Building is a two-story wood frame building topped by a cupola. The Academy Building was built as a college preparatory school for boys. It went through several changes before becoming home to the coeducational Gorham Seminary in 1856. This school closed in 1877 and the building was leased to the state for use as part of the normal college (now USM) that had been built around it. The facade features an elaborate entry porch supported by four Doric columns and topped by a railing.

Oriented towards Robinhood Cove, the Benjamin Riggs House is located in rural Georgetown. The Federal-style house is two-stories tall with a low-pitched hipped roof and a large central brick chimney. Its front facade is symmetrical with a central entry evenly placed between two windows. It has a rear ell that extends to a carriage barn (a nineteenth century addition). The paneled front door is topped with a fanlight and accented with pilasters and projecting cornice. Benjamin Riggs was born in Gloucester, Massachusetts, and arrived in Georgetown in 1776.

The Parker House located southwest of Blue Hill proper, is a two-story, hipped roof, Federal-style structure. The symmetrical dwelling is clad in narrow clapboard siding and with a central door set under a slim entablature and framed by narrow pilasters and sidelights. The house sits on a granite foundation and has windows composed of numerous panes of glass. At the turn of the twentieth century, the house was remodeled by Blue Hill native, architect George Clough.

Located in a rural area between Hartford and Buckfield, the David Warren House is a rare early nineteenth-century example in this area of a large Federal-style house. The building is two stories with a side-gabled roof and two interior end brick chimneys. The house has a centrally placed front entry with a classical door surround consisting of wide pilasters supporting an entablature and projecting cornice. A four-light transom sits above the door. A side ell connects the house with a gable-front barn.

Union, Maine, was settled between 1772 and 1776 and incorporated in 1786. Like many inland towns in the region, the population steadily grew after the Revolutionary War and into the early decades of the nineteenth century as people moved to the rural areas of Maine for the opportunity to build homesteads and establish livelihoods. The Common in Union is a town-owned green space that became a community space. The first record of the Common dates to 1790, but the land was not deeded to the town until 1809.

After his sea captain father died, young Nathaniel Hawthorne, his mother, Elizabeth, and siblings moved from Salem, Massachusetts, to Raymond where his uncle Richard Manning had also relocated to manage his family's land holdings. Manning built this house for Elizabeth and her children just down the street from his own home. The wood framed house is two stories tall, with clapboard siding and a side-gabled roof. The facade is symmetrical with a central entry.

The Boynton Street Historic District, in Eastport, includes three Federal style homes dating from 1810-1822: Weston House (1810), Kilby House (1820), and Stetson-Starboard House (1822). Each are similar in materials and layout: two stories high with low-pitched hipped roofs and clapboard siding. Each front facade has a central entry with distinctive doors. Federal-style residences are not common in Eastport, and this represents the finest concentration of this style east of Machias.

During the early nineteenth century settlements in Maine began to lose their frontier characteristics as civic improvements created more structured communities. These improvements included the regulation of livestock. During early settlement, many areas in Maine were largely agricultural and animals including swine, horses, cattle, and sheep were allowed to roam free. As infrastructure improved, it became a health hazard and a nuisance to allow this practice to continue.