Deer Island is a small island located in Boston Harbor, Massachusetts. It covers approximately 185 acres and is part of the Boston Harbor Islands National and State Park. The island is primarily known for its role in wastewater treatment, housing the Deer Island Wastewater Treatment Plant, which serves the greater Boston area. In addition to its industrial use, Deer Island offers recreational opportunities. Visitors can enjoy scenic views, walking trails, and birdwatching. The island is accessible by ferry and is a popular spot for those looking to explore the natural beauty of the harbor while learning about its environmental significance.