The northern half of a Casco Bay island once known as the “Ellis Island of the North” has sold for $4.5 million.

The sale of 12 acres on House Island to Portland entrepreneur Noah Gordon closed last week, said Ana Piper, a marketing manager with the David Banks Team of Re/Max by the Bay. She said the portion of the island that was sold had been owned by two companies that rented the island and three cottages for weddings and other events.

The property includes a four-bedroom main lodge, a slightly smaller four-bedroom house and a two-bedroom cottage. The buildings had been used as a detention center, a home for a public health officer and a small hospital when House Island was known as the “Ellis Island of the North,” with a federal immigration quarantine center operating on the island from 1907-1937.

The rest of the island, covering 16 acres, is owned by the estate of Michael Scarks, a Portland developer who died in 2015, Piper said.

Scarks had purchased the northern half of the island for $2.5 million and the largely undeveloped southern half for $500,000. In 2014, Scarks sold the northern half of the island to Vincent and Christina Mona, who in 2017 said they planned to use the property to host weddings, corporate retreats and other events. They operated under the corporate name Three Palms Design Build.

Scarks said he planned to develop luxury vacation homes on the island, which is part of Portland and alarmed preservationists in the city. He died before his plans could advance.

David Banks said the Monas have since relocated full time to Florida and put their portion of House Island on the market. They are in their 70s, he said, and plan to concentrate on developing their properties in Florida.

Banks said the plan to rent out the island had been going well. He knew of three couples that had weddings on the island this year, he said, and Mercedes-Benz held a corporate event there.

A cottage on House Island is part of the property sold for $4.5 million to Noah Gordon, a Portland entrepreneur. The property once housed a complex to treat quarantined immigrants, earning it the nickname “Ellis Island of the North.”

Gordon, 45, hopes to build on the Monas’ vision, saying he plans to turn House Island into “the premier private island hospitality event venue in America.” He didn’t provide details on what that might entail.

Gordon grew up in southern Maine and graduated from Georgetown University before starting Jaze, an automotive diagnostics firm. He also owns Coastal Maine painting.

The southern half of the island is home to Fort Scammell, the only fort on the Maine coast to see action in the War of 1812, firing at British privateers trying to steal a sloop. The British fired back, but no one on either side was hurt.

After the war, it was used for decades by two fishing families to process groundfish before the federal government established the quarantine center.

The city’s Historic Preservation Board last year approved plans for a 21-site campground near Fort Scammell.

Sarah Hansen, the executive director of Greater Portland Landmarks, said her organization will watch plans for the island under its new owner closely.

In 2012, House Island was named to the organization’s “Places in Peril” list because it was not covered by any historic or preservation designations. In 2015, the city of Portland designated the island a local historic district, which gives the city greater oversight to preserve “existing historic buildings, structures and landscape features.”

Although the designation doesn’t bar future development, she said, it does mandate that most plans go through the city’s Historic Preservation Board. That body seeks to moderate the impact of new development on historic structures by reviewing the scale and materials used in any new project, Hansen said.