Cow Island is a 26-acre (11 ha) island in Casco Bay, Maine, United States,[1] off Great Diamond Island, about 3 miles (4.8 km) northeast of downtown Portland, and is part of the Town of Long Island in Cumberland County. A non-profit youth development organization called Rippleffect owns the island and has the responsibility to protect the island's natural ecosystem as well as the island's public access. [2]