A $200 million addition at the present museum site, which will be larger than the heralded 2003 wing designed by architect Moshe Safdie, will greatly enlarge gallery space while adding a new restaurant and roof garden.

"When we finish this project in 2016, our total gallery space will rank among the top eight or 10 American art museums," said Monroe, also the museum's CEO.

The PEM's earlier expansion helped spark millions of dollars in private investment in the city and a downtown renaissance. There are similar hopes for these plans.

"For a city the size of Salem, a $200 million investment is significant and will certainly have a positive impact through the downtown and city," Mayor Kim Driscoll said. "I'm thrilled they have the confidence in Salem's direction ... to make this type of investment."

The $650 million fundraising campaign is well under way. Monroe announced that $550 million has already been secured in gifts and pledges.

Unlike 2003, when the PEM had to acquire a city street and move several houses, there are no plans this time to take any land.

"We're going to work on our existing footprint," Monroe said.

Sections of the museum that are old and outdated will be removed along with the power plant on Charter Street. In effect, a large part of the museum will be gutted.

"In the end, it's clear that it's just not viable to try to renovate and restore ... buildings built, in some instances, in the 19th century ..." Monroe said.

The heart of the PEM, however, will remain.

"Obviously, East India Marine Hall will not only remain intact, but will end up having a much bigger presence," he said.

Also remaining are a main section of the museum along the Essex Street pedestrian mall and the Safdie addition, which includes two floors of galleries, a cathedral entrance and atrium, and Yin Yu Tang, a 200-year-old Chinese house.

There are also plans to make improvements across the street at the Phillips Library.

The museum plans to remain open throughout construction, Monroe said.

The idea behind the expansion, the executive director said, is to create more state-of-the-art galleries and other spaces so the museum can initiate and host more exhibits, showcase more of its own vast collections, and increase the number of education and public programs.

"The real driver from the standpoint of gallery space is that we have some Class A gallery space now and other gallery space that really doesn't meet those standards and really is not ideal," he said.

While the proposed construction may draw the most public interest, the PEM started this drive several years ago to bolster its financial stability, fund needed improvements and advance its mission.

"We're building for the long-term," Monroe said.

The Advancement Campaign will inject $350 million into the museum's endowment, boosting it to $630 million, which will put it in the top six of American art museums in total endowment, according to the PEM.

Monroe credited the hard work of the museum's staff and generosity of its donors with the success to date. He declined to name major donors, but said many of the backers are local.

"When you look at Massachusetts and what it has done in terms of philanthropy for art over the past decade, it's really quite remarkable ..." he said.

"Obviously, we're extremely happy and gratified with the support we've received. It's really a tribute in part to the legacy we have built upon (over 212) years. But, in part, it's being very innovative and setting ambitious goals and achieving them."

The successful 2003 campaign, when the Safdie wing was built, raised nearly $200 million.

Monroe announced these new plans at the museum's Saturday night gala, Reves de Paris, a 1920s dinner-dance in the museum's atrium.

Although 2016 is the goal for completing the campaign and expansion, Monroe said there is not yet a construction timetable or start date.

The expansion is complex, he said, and will be done in phases.

The 175,000-square-foot expansion will be designed by Rick Mather Architects of London, which, among other projects, worked at the National Maritime Museum in Greenwich, England, and the Virginia Museum of Fine Arts.