Cow Island is a 26-acre (11 ha) island in Casco Bay, Maine, 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. Ironically, the main export of Cow Island was goats' milk. The west side of the island is public land, and allows camping.