Several of the Porcupine Islands are visible off the coast of Maine in this view from the summit of Cadillac Mountain. From right to left, the islands are Bald Porcupine Island, Long Porcupine Island, Burnt Porcupine Island (and Rum Key), and Sheep Porcupine Island. Stave Island is also visible along the oppose coast on the right side. Several of the Porcupine Islands have relatively gentle slopes on their north sides and steep drops on the south. Like much of Acadia National Park, they were carved by retreating glaciers.