Back Street is a historic street in Boston, Massachusetts. During the colonial era, the street ran from Middle Street in the southwest to Princes Street in the northeast. It served as an alley to access the back of Beacon Street's houses during the late 19th century. In 1910, the Charles River Esplanade was completed along the banks of the Charles River, and more land was reclaimed from the river to build Storrow Drive, putting 250 feet between Back Street and the river.