Built under the orders of George Washington, the Portland Head Light is one of four remaining lighthouses authorized by the first president. Set high on a rock promontory jutting out into Casco Bay, it is used by mariners for guidance to this day. The tower is constructed of stone rubble from its base to a stone ledge. The top section of the tower above the ledge is made of brick. In addition to the light tower, the site also contains the keepers' quarters (1891), whistle house (rebuilt in 1975), paint locker, and garage. The tower room and whistle house are constructed of stone and brick.

Hall's Tavern is one of the oldest buildings in Falmouth. Constructed by Nicholas Hall, the house was first used as a private residence until its conversion into a tavern by Nicholas' son Onzi Hall some twenty-five years later. While the building's exterior clearly exhibits a fine Federal-style design, much of Hall Tavern's unique historic value lies in its interior: a historic taproom and bedrooms with finely-stenciled wall designs remain largely unchanged from the earliest years of its use as a tavern.

Likely the second oldest brick school in the state (one in Winslow is thought to be older), Dresden's Brick School House is located in a rural area near the Kennebec River. It is a rectangular one-story brick, front gabled building. The facade faces the road and contains two entry doors and a window in the gable end that has been filled. Each door is topped by a narrow transom window. An interior chimney sits close to the front of the building. The north and south elevations each contain two sash windows to allow light into the school house.

The Joseph and Hannah Maxcy Homestead is located on South Union Road. Joseph Maxcy moved to the area from Attleboro, Massachusetts, in 1788. The first European settlers arrived fifteen years earlier, but a town had yet to form. Maxcy initially cleared the land and was later joined by his brother, Benjamin. The brothers quickly purchased land near Crawford Stream and built a saw and grist mill. Like many rural communities in Maine, milling was a fruitful venture and their success became the impetus for developing the town of Union.

A National Historic Landmark, Fort Halifax Blockhouse was erected as part of Fort Halifax. The blockhouse is the oldest extant wooden blockhouse in the country and the only surviving element of the fort structure. It is built of hewed logs with dove-tailed and pegged joints. It is approximately 20' square and two stories high with an overhanging second story and a hipped roof. Located at the confluence of the Kennebec and Sebasticook Rivers, the fort was built by English settlers in 1754 to protect colonial settlements along the Kennebec.

The Lincoln House, located on Main Street, is likely the oldest surviving building in the town of Dennysville and dates from the first settlement of the area in the late eighteenth century. The side-gabled house sits on a mortared fieldstone foundation and is covered with clapboard siding. The structure is two stories with a central doorway topped with a triangular pediment. The home was built by master builder Joshua Chubbuck for Theodore Lincoln.

The Adams-Cate House, located in Castine, is a two-story Federal-style home notably known its curved interior hall with a curved door and staircase. The exterior of the house includes an elaborate elliptical fanlight and sidelights around the front entry that allows the maximum amount of light into the house during the long dark winter months. The original owners, Thomas and Jane Adams, built the house in 1815. Thomas was a businessman, selectman, and Representative to the General Court of Massachusetts. Their daughter, Jane Elizabeth Cate, also raised her family in the home.

The Alfred Shaker Historic District encompasses buildings from the eighteenth, nineteenth, and twentieth centuries. Located on Shaker Hill Road, the area is approximately 300 acres. It sits on a hillside and is bordered by stone walls and forested lands. Development of the area began in 1793 with the construction of a Meeting House. Soon after, several two-story dwellings, shops, and agricultural outbuildings dotted the landscape. There are twenty structures in total.

One of Portland's few surviving Federal period homes, the William Minott House is a three-story wood frame structure. Clad in flush tongue-and groove boards on the facade and clapboards on the other elevations, it has a low-pitched hipped roof with two chimneys on either end. The facade is symmetrical with a central entry door. The door is framed by sidelights and topped with an ornate elliptical fanlight. Above the door on the second floor is a three-part rectangular window.

The Blackhawk Putnam Tavern, a two-story house in the Federal style, overlooks the town of Houlton at the intersection of US Route 1 and US Route 2. Purportedly the oldest wood frame building in Aroostook County, it also features Greek Revival-style elements such as pilasters and an entablature. It's distinctive portico, or porch, was added in the early twentieth century. It was built in 1813 for Aaron Putnam by master carpenter Amos Wormwood of Alfred. Located near the Military Road (Route 2), which was completed in 1828, the house also operated as a tavern.