Old Post Office (Liberty, Maine) is located in Maine

The Old Post Office, also known as the Old Octagonal Post Office, is an historic octagon-shaped former U.S. post office building located on Main Street in Liberty, Maine. The town of Liberty boasts that the building, which was built in 1870, is "the only octagonal post office in the United States". 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.^[3] On June 19, 1973, it was added to the National Register of Historic Places.

• http://en.wikipedia.org/wiki/Old Post Office (Liberty, Maine)