Dan Monroe, who’s led Peabody Essex Museum for 25 years, will retire in 2019

Dan Monroe has overseen a period of impressive growth during a 25-year tenure.Lane Turner/Globe Staff

Dan Monroe, the forward-thinking chief executive of the Peabody Essex Museum for the past 25 years, announced Thursday that he will retire next September.

The museum has experienced extraordinary growth with Monroe at the helm. When he was hired, in 1993, PEM had an annual operating budget of $3 million and an endowment of $23 million. Today, the operating budget is more than $33 million, and the endowment more than $500 million.

Monroe, 74, has put PEM on the world stage. The museum is among the top 10 percent of US and Canadian museums, by several metrics. It has partnered with institutions internationally, such as the Palace Museum in Beijing and London’s Victoria and Albert Museum, to mount major traveling exhibitions.

He attributes PEM’s success to its mission. “It’s a commitment to creating experiences of our culture that transform people, changing the way they see themselves and their world,” he said in a telephone interview Tuesday.

When he took the job, two history museums, the Peabody Museum of Salem and the Essex Institute, had just merged.

“The discussions about the two getting together had gone back well over 100 years before that,” said Robert N. Shapiro, president of PEM’s Board of Trustees, in a telephone interview Tuesday. “We do continuity in Salem.”

PEM’s history goes back to 1799, when the East India Marine Society was founded with a charter to establish a “cabinet of natural and artificial curiosities,” brought home to Salem by sea captains traveling the world. It’s the oldest continually operating museum in the United States. The collection of 1.8 million art objects is one of the largest in the country.

Monroe, who had worked as a commercial fisherman in Alaska, came to PEM from the Portland Art Museum. He had helped to write federal legislation about the repatriation of Native American human remains and cultural objects. He arrived in Salem with a vision that would prepare PEM for the 21st century.

“We needed to change almost everything,” he said.

He insisted that no objects could be classified ethnologically, prompting a reorganization of the collection.

“We couldn’t continue the 19th-century hierarchy of fine art, which puts Western European white male artists at the pinnacle of human expression,” he said.

PEM’s physical plant has expanded during Monroe’s stewardship, starting with a 113,000-square-foot addition in 2003. This year, the museum opened a 120,000-square-foot Collection Center in Rowley. The move of historic local documents to another town sparked an outcry from Salem residents.

Next year, a new 40,000-square-foot wing will highlight the collection in fresh ways based on neuroscience research — last year, Monroe established a neuroscience initiative at PEM.

“There was a mission and a vision at the start, but gosh, we didn’t know where we’d be 25 years hence,” Shapiro said.

Monroe developed a new financial model for art museums focused on a heftier endowment, which has helped drive the growth. The museum’s current fund-raising effort, the $650 million Connect Campaign, allots $350 million to the endowment, $200 million to expansion, and $100 million for infrastructure.

“Having an endowment provide twice as much as average for operating support provides a more stable financial base,” he said. “Instead of raising money to keep the lights on, you can invest more in creative and innovative projects.”

The Connect Campaign kicked off in 2011, and more than $600 million has now been raised.

“Boston doesn’t get its due in terms of philanthropy,” Monroe said. “We’re working with venture philanthropists, who want to create something entirely new.”

Shapiro said that from the start, Monroe’s focus has been on PEM’s visitor experience, and he has advocated for clever, engaging exhibition design. The neuroscience initiative, headed by neurobiologist Tedi Asher, puts research about how the brain works into that process.

“Empresses of China’s Forbidden City,” on view through Feb. 10, is an example.

“There’s consciously a flow. You turn corners, be surprised, and encounter a small group of objects in a small space,” Shapiro said. “It kicks the brain from fast brain to slow brain, to cause people to pause, absorb, and reflect.”

After Monroe retires, he plans to move with his wife to Santa Fe, where he will write and consult.

He may have brought a strong, flexible vision to PEM, but he attributes the museum’s remarkable growth to his team. “All the things we’ve done are the work of incredibly talented staff, volunteers, Board of Trustees and Board of Overseers, patrons, and philanthropists,” he said. “They are the people who make things happen, and the credit for what has happened belongs to them.”