The smallest town in Franklin County, Monroe, lies in the farthest northwestern corner of the county. It is sometimes called Monroe Bridge because once the Hoosac Tunnel and Wilmington Railroad were completed, crewmen were told to leave the town’s mailbags at the Monroe bridge. In 1888, the post office was established and was known as the Monroe Bridge Post Office.
The town's eastern border with Rowe is along the Deerfield River. It is bordered by Vermont to the north and the town of Florida to the south and west.