The Edgartown National Bank, the Island’s second oldest bank whose charter dates to 1905, will be acquired by the Rockland Trust Company.

The announcement was made in a joint press release after the close of business Thursday and also in a full-page advertisement in Friday’s edition of the Gazette.

The merger has been approved by boards at both banks and is expected to be complete by May 2017, pending an array of regulatory approvals. The transaction is valued at about $24.5 million.

The name of the bank will change to Rockland Trust once the merger is finalized.

Long headquartered in the historic brick building at Four Corners in downtown Edgartown, Edgartown National has three branch offices and about 40 employees. Its parent holding company, Island Bancorp Inc., has $194 million in assets.

Founded in 1907 in the Boston suburb of Rockland, Rockland Trust is wholly owned by Independent Bank Corp, with $7.5 billion in assets. The trust has expanded rapidly in recent years, completing the acquisition of Bank of Cape Cod just this week.

At a small gathering Friday morning that included members of the Island press, leaders at both Edgartown National and Rockland Trust said the merger is the result of several months of talks that came at the initiative of the smaller Edgartown bank.

“It was part of our strategic plan,” Edgartown National president and chief executive officer Fielding Moore told the Gazette. “We’re into the 21st century, risk management systems are required and we would need to be a bank twice our size to be able to have all the resources needed.”

“Banks are sold, not bought,” said Rockland president and chief executive officer Christopher Oddleifson, noting that the two community banks have much in common, beginning with a strong focus on customer service.

As part of the change, Mr. Moore, who indicated he is nearing retirement age, said he will step down, working as a consultant during a transition period.

All customer-facing staff including all branch employees will be retained, Mr. Oddleifson said, as will two senior vice presidents, Dee Lander and John Washbrook. Up to 20 employees who work in the main office will be transitioned out or offered different jobs within Rockland Trust. Every employee whose job is slated for elimination will be given priority for open positions in Rockland banks, including on the Cape, he said. Rockland employs more than 1,000 people.

Bank leaders talked about the many advantages the merger will bring, from increased lending capacity, mobile banking options and additional services for commercial and residential clients. (Edgartown National currently has a loan limit of $2.5 million, while Rockland’s loan limit is $100 million, Mr. Oddleifson said.) Rockland also plans to offer wealth management services through its own established wealth management division, a service Edgartown does not currently offer.

Mr. Oddleifson also spoke about Rockland’s rapid expansion. The trust has been on a buying spree since 2008 and now boasts more than 85 branches in eastern Massachusetts and Rhode Island. Between 2008 and 2015 it acquired Slades Ferry Bancorp, Benjamin Franklin Bank, Central Bank, Mayflower Bank and Peoples Federal Savings Bank. Rockland received final regulatory approval this week to acquire Bank of Cape Cod, a small community bank with assets of $260 million that operates four branches in Hyannis, Falmouth and Osterville. Plans call for Rockland Trust to close three out of the four of those branches but absorb most of the existing staff.

“We’re on a roll, “ Mr. Oddleifson said, adding: “I think the sort of Goldilocks size is where we are headed — between $15 and $20 billion. My sense is at anything bigger than that it become difficult to for senior managers to view the employees as human beings.”

The merger announcement opens another new chapter in the changing story of banking on the Vineyard. Twenty years ago the Vineyard had four banks, all independently owned. In 1994 the Martha’s Vineyard National Bank, founded in 1885, merged with Compass Bank. Compass later merged with Sovereign Bank, and in 2009 Sovereign was acquired by the global banking giant, Santander. Meanwhile, in 2007, the Martha’s Vineyard Cooperative Bank and Dukes County Savings Bank merged to become the Martha’s Vineyard Savings Bank. Last spring, Cape Cod Five Cents, an independent bank based in Orleans, opened a full-service branch in Vineyard Haven. Only the Edgartown National has remained unchanged — until now.

“It is a natural expansion and strengthening of our Cape Cod franchise,” Mr. Oddleifson said in the press release of the Vineyard transaction. “Edgartown National and Rockland Trust share the same values, and are committed to the communities they serve and the families that live in them,” he added.

“We are extremely pleased to join Rockland Trust, a growing bank with a terrific brand,” said Mr. Moore in the release.

The Edgartown bank has a rich legacy of community involvement. In 1955 on the occasion of its 50th anniversary, the Gazette dubbed the bank the Old Lady of the Four Corners, playing off the bank of England’s nickname The Old Lady of Threadneedle Street.

In 1967 the bank became the first to open a streetside teller window on Main street in Edgartown. In 1975 it made another first by offering free checking accounts. In 1987 the bank embarked on a $500,000 expansion, renovation and modernization of its main office in downtown Edgartown. “The heart of Edgartown will always be home for Edgartown National Bank,” the bank said in a large advertisement in the Gazette that year.

Members of the Vose family have long played a leading role at the bank, among them Donald Vose whose served as the bank’s president for 51 years. Mr. Vose died in 2008.

In a show of commitment to the Vineyard community, Rockland will donate $25,000 to the Island Housing Trust; a check passing ceremony was held Friday morning with IHT executive director Philippe Jordi.

In terms of total assets, Rockland is more than twice the size of Cape Cod Five and 10 times larger than Martha’s Vineyard Savings Bank. Santander is by far the largest Island bank, with $54.7 billion in deposits in the U.S. alone.

But based on Island deposits, Martha’s Vineyard is clear market leader, with 45.5 per cent market share at the end of June, according to the federal Federal Deposit Insurance Corporation. Edgartown National had a 14 per cent market share.