Cliff Island is an island in Casco Bay Maine. It is part of the city of Portland, Maine. As of the 2000 census, the island had a year-round population of approximately 60 people. In the summer, the island's population grows to about 200, despite the fact that it is the only year-round inhabited island in Casco Bay with no paved roads. Originally named Crotch Island for its H-shape and natural harbors, the name was changed to end mail mix-ups with several other islands in Maine.
In the early 20th century the island's inns were a draw for summer tourists. There are no hotels any longer, but many homes are available for weekly rentals or longer. While there are no public services, residents enjoy a community hall, a tennis court, baseball field, and playground. The residents are served by a USPS Post Office, fire department, and one-room school for elementary grades. While the postal service has considering closing the office in the past, the islanders have managed to keep it in operation for six hours a day.