New owners of a landmark high-rise in downtown Portland plan to invest millions of dollars in overdue improvements and maintenance and lease high-end offices in the heart of Monument Square.

The landmark building at 465 Congress St., Portland’s first skyscraper, has been sold to investors. AReynolds photo

Alta Properties of Newton, Massachusetts, and Connecticut River Capital of Lebanon, New Hampshire, bought 465 Congress St., commonly known as the People’s United Bank Building, earlier this month.

The nearly 100-year-old building, at the corner of Congress and Preble streets, was Portland’s first skyscraper. It features lavish details such as a marble-accented lobby with vaulted ceilings and pillars, ornamental accents on its limestone exterior and expansive views.

“It is a beautiful building,” said Kathleen Kusiak, managing partner at Alta Properties. But the 10-story building is 60 percent vacant and needs significant upgrades to the lobby and elevators, exterior facade and ventilation systems.

“Not too long ago, it was 100 percent full,” Kusiak said. “The building is liked by tenants, it just hasn’t been properly managed, we think it is not going to be too hard to get it back to where it should be.”

Kusiak would not say how much the companies paid for the building or their precise renovation budget. A $9.2 million mortgage on the building was filed June 6 with the Cumberland County Registry of Deeds.

The building was last purchased in 2013 by local developer Joseph Soley for $5.5 million, according to city records.

This is the first acquisition in Maine for both companies. Portland’s economic growth and demand for office space attracted them to the market, Kusiak said.

Alta Properties’ portfolio includes office buildings in Maryland, Massachusetts, Vermont and New Hampshire. Connecticut River Capital has buildings in Vermont, Massachusetts and New Hampshire.

The owners envision offices that mix clean modern design and the building’s historic character, said Nate Stevens, a broker with The Boulos Co. in Portland. Stevens and Jon Rizzo from Boulos are leasing agents for the property.

High-end offices in Portland are at a premium, with almost no vacancy for any Class A office space, Stevens said. The idea is to create something that is still high-end, but unique and at a little lower price than nearby offices.

“What these buyers are really aiming to do is create a niche in the market to produce a really nice product,” Stevens said. “There is a market for that and it doesn’t really exist in Portland.”

Although construction prices are at a 10-year high, the new owners have the resources and determination to get new offices ready by early next year, Stevens said.

The owners consulted with the nonprofit preservation group Greater Portland Landmarks after purchasing the building and reviewed old records and photographs, said Executive Director Hilary Bassett.

She was pleased the present owners take an interest in the building’s significance and want to maintain its character, Bassett said.

“This was definitely a building that was made to be impressive,” she said. “We always like working with developers who are interested in preservation and we look forward to helping them connect with contractors who can help with that,” Bassett said.