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In the 18th century, Great Diamond Island was a private island owned by Deacon James Milk, who farmed and enjoyed the natural beauty of “Great Hogg Island,” followed by his heirs the Preble, Fessenden and Deering families. While the owners allowed Diamond Cove on the northerly end to be used for picnics and recreation, the island remained exclusively private until the US military purchased land on either side of Diamond Cove in 1873.


In 1882 an enterprising group of men from Portland, Maine, purchased from Henry Deering a large tract of land (approx. 245 acres) extending from Diamond Cove to the southwesterly segment of the island. It was their intention to establish a self-sufficient, planned community.  So they sold lots, established the Diamond Island Association, and changed the island’s name from Great Hogg (perhaps an indication of its former agricultural use) to Great Diamond Island, based partly on the ample supply of quartz crystals found on the island, but also surely to entice others to become property owners in the Diamond Island Association.  They had great plans for the island which included building their own wharf, the Casco Wharf; purchasing their own forty-five foot steam boat, the Isis; leasing the existing farm to furnish their own produce; establishing roads and areas for parks; setting up an acetylene gas production plant; erecting kerosene street lamps; establishing a water supply system; building a restaurant and meeting hall for association members; establishing a community store; and devising a set of by-laws which dictated how things would be.  A grand plan indeed!  

Today, approximately 100 acres of original Deering property at the southern end of the island remain privately owned, and about 200 acres at the northern end are also owned privately by Diamond Cove Homeowners’ Association. 


A more complete history of Great Diamond is available at The Store at Elwell Hall. There also are annual history exhibits at Elwell Hall and at the Museum at Diamond Cove.



The Diamond Cove Homeowners Association (DCHA), formerly historic Fort McKinley, covers approximately 193 acres on the northern end of Great Diamond Island. The Fort was constructed by the US government between 1891 and 1906 and was designed to defend Portland Harbor during the Spanish American War. Originally, Fort McKinley consisted of the traditional Endicott style fort surrounding a military parade ground and was home to over 1000 soldiers and their families. In 1949, the US Army declared Fort McKinley surplus and it sat vacant for over 40 years. In 1961, the fort was sold to a private developer. It was not until 1984, when the property was in a state of dire disrepair, that restoration was begun by DicTar Associates. The restoration was met with a great deal of public controversy over access and environmental impact – CBIA, Audubon, Conservation Law of Boston, and The Island Institute advocated for and succeeded in limiting the number of units approved, protecting open spaces in the Cove and limiting intra-island traffic. The residential project was ultimately finalized by McKinley Partners into the residential community that exists today. There are over 100 private residences, 2 seasonal restaurants and a seasonal hotel. The restored property has preserved an historic era of US and island history, and is listed on the National Historic Registry. Guided tours are available to the public. A small museum facility is also open by chance or by appointment.To arrange tours and access to the Museum contact:





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