Harbor Island is a small, heavily wooded island at the mouth of the New Meadows River across from the shores of Sebasco in Phippsburg, Sagadahoc County, Maine, United States. There are two beaches on the island, one on the south end just across from Sebasco Harbor Resort, the other a small sandy cove on the north end. There are a few private h…Harbor Island is a small, heavily wooded island at the mouth of the New Meadows River across from the shores of Sebasco in Phippsburg, Sagadahoc County, Maine, United States. There are two beaches on the island, one on the south end just across from Sebasco Harbor Resort, the other a small sandy cove on the north end. There are a few private homes on the island.