House Island is a private island in Portland Harbor in Casco Bay, Maine, United States. It is part of the City of Portland. The island is accessible only by boat. Public access is prohibited, except for an on-request tour sanctioned by the island's owners. House Island includes three buildings on the east side and Fort Scammell on the west side. The buildings are used as vacation rentals and other summer residences. The island's name derives from the site of an early European house, believed that built by Capt. Christopher Levett, an English explorer of the region. The island sold for $5.35m in 2022. Fort Scammell Henry A. S. Dearborn, an officer of the Massachusetts Militia and a future general, built Fort Scammell on the island in 1808 as part of the national second system of fortifications. It was named after Alexander Scammell, Adjutant-General of the Continental Army during the American Revolutionary War, who was killed in action during the Battle of Yorktown. (The middle names of the fort's builder were also chosen after Scammell, a friend of the builder's father, Secretary of War Henry Dearborn.) The fort was designed for harbor defense, with cannon batteries designed to protect the main shipping channel into Portland harbor, along with Fort Preble. The spelling of the fort's name varies among references. The fort was made of stone, brick, and earth, and initially mounted fifteen guns and a 10-inch mortar. The Secretary of War's report on fortifications for 1811 describes Fort Scammell as "a circular battery of masonry with circular flanks, mounting fifteen heavy guns, is covered in the rear with a wooden blockhouse, mounting six guns...". Typical weapons of the period were 24-pounder or 32-pounder smoothbore cannon. In the 1840s–1850s, as part of the national third system of fortifications, Fort Scammell was modernized by extending its walls to enclose a larger area. Thomas Lincoln Casey, an Army engineer officer known for his work on the Washington Monument, completely rebuilt the fort beginning in 1862 during the American Civil War. As rebuilt to the new Third System design Fort Scammell was unique in the US, with the design centered on two three-tier stone-and-brick bastions connected by earth walls rather than stone curtain walls. A third bastion was never completed. To allow timely completion, the remaining bastions had a tier or two each removed from the design. As completed, the west bastion had a single