Groton – Charter Oak Federal Credit Union reported today that 2011 was “the strongest year in its history,” with profits hitting a record $8.4 million.

Charter Oak, which held its 73rd annual meeting last week at the Groton Inn & Suites, said profits rose more than 70 percent from the $4.9 million recorded the previous year. The credit union’s assets now exceed $700 million for the first time.

Chairman Guy Henry of Oakdale said during the annual meeting that Charter Oak is expanding its market share in New London and Windham counties. Brian A. Orenstein, Charter Oak’s chief executive, said the financial institution’s Gold Rewards program that has given back $531,000 to members over the past two years in $100 installments has been a tremendous success.

“It’s our way of saying thank you for your business,” Orenstein said in a statement.

Orenstein said Charter Oak’s new branch and corporate headquarters at 1055 Hartford Turnpike in Waterford, to begin construction this year, will continue a nearly four-decade trend of expansion at the credit union.

“When we moved into (the current) Chicago Avenue (headquarters in Groton) in 1974, the credit union had assets of $25 million,” he said. “Today, we have grown to more than $700 million – or 28 times that size.”

Among the credit union’s milestones last year was the opening of its 12th office at General Dynamics’ Electric Boat campus in New London.