Rainsford Island, formerly known Hospital Island, Pest House Island, and Quarantine Island, is a 11-acre (45,000 m2) island in the Boston Harbor, situated between Long Island and Peddocks Island. The island is composed of two drumlins, reaching an elevation of 49 feet (15 m) above sea level. The shoreline is predominantly rocky with a sandy cove in the south side, and a variety of wildflowers abound. Access is by private boat only. Since 1996 it has been part of the Boston Harbor Islands National Recreation Area.

Boston Harbor is a natural harbor and estuary of Massachusetts Bay, and is located adjacent to the city of Boston, Massachusetts. It is home to the Port of Boston, a major shipping facility in the Northeastern United States.