BATH — Maine Maritime Museum is taking over the Portland Harbor Museum and will broaden its programming in greater Portland.

Amy Lent, executive director of the Maine Maritime Museum, said Tuesday that the Portland museum’s collections should be completely transferred to 243 Washington St. by the end of the summer.

“We’ve been preparing for this for some time, and we’ve been making room,” Lent said of the merger that took effect June 1.

She said the Portland museum has had several homes, most recently at 510 Congress St. in Portland.

While the museum faced challenges in sustaining itself financially to take care of its space and collections, “they always had really outstanding programs,” Lent said. “The great thing about this merger is that … their programming will continue in Portland and the greater Portland area.”

Through the merger, which has been more than a year in the making, the Portland museum’s approximately 500 members automatically become Maine Maritime Museum members.

Lent said the Portland museum had been using its Congress Street space rent-free, but the building has been sold.

“They were going to have to vacate that space eventually and did not have another permanent home lined up,” Lent said.

Programs are planned for places such as the Portland Public Library and the University of Southern Maine’s public lecture spaces, Lent said.

“We’ve been successful here in Bath partnering up with other non-profits and offering lectures that kind of extend beyond our immediate membership, so we hope to do the same kind of thing in Portland,” she said.

Mark Thompson, who has served as the Portland Harbor Museum’s executive director, has joined the Bath museum staff as its regional director in southern Maine. He will organize programming and outreach in greater Portland.

“Our collections are going to be under the expert care of the curatorial staff in Bath,” Thompson said Tuesday, adding that southern Maine members will be offered more programming than before.

He also said the merger will “bring a great deal of stability and ensure that the work that we’ve done to fulfill our mission continues, and that’s really what it’s about.”

This kind of cooperative initiative is what all non-profits will have to do to sustain themselves, Thompson said. “We all need to take a creative look at ways that we can more efficiently serve our constituency,” he said, “and that’s essentially what we did here.”

Lent said she hopes ultimately to have off-site exhibits in the Portland area, in order to keep “as much of the Portland maritime story accessible as we can.”

The merger’s southern Maine programming will cater to current Maine Maritime Museum members who live in the Portland area, she said, and the Portland collections fill voids in the Bath inventory, including artifacts and documents about the Liberty ships built in South Portland during World War II.

Alex Lear can be reached at 373-9060 ext. 113 or alear@theforecaster.net.