The town of Liberty boasts that the building, which was built in 1870, is "the only octagonal post office in the United States".

[2] The building, which "has all its original equipment" is now the home of the Liberty Historical Society, which opens it to the public on Saturdays during the summer.

The Old Post Office is located in Liberty's village center, set close to the south side of Main Street (Maine State Route 173), two doors east of the public library.

It is a small single-story eight-sided wood-frame structure, covered by a low-pitch octagonal roof and clapboard siding.

It served as the town post office in 1960, and is now maintained as a museum by the local historical society.