After 36 years with South Portland propane and heating oil provider Dead River Co., Deanna Sherman has announced she will retire as president and CEO at the end of June and transition to the role of senior adviser.

Deanna Sherman Photo courtesy of Dead River Co.

Dead River Chief Operating Officer Casey Cramton has been chosen as Sherman’s successor, the company said Thursday. Cramton has been with the company for 35 years.

During Sherman’s tenure, Dead River has become the largest heating company north of Boston, with local offices in Maine, New Hampshire, Vermont and Massachusetts, the company said in a news release. Dead River now has more than 1,100 employees. The privately held company said it does not disclose annual revenue figures.

After joining the company in 1986, Sherman moved steadily up the ranks to district manager positions, then regional manager, and then vice president of the firm’s energy division before being named president and CEO in 2016.

“It is a true privilege to work and live in Maine, and an honor to lead one of Maine’s oldest and largest employers,” Sherman said in a statement. “Working with such a dedicated team of people for so many years has been immensely rewarding, both professionally and personally. I am now looking forward to enjoying my newfound time and flexibility with my family and friends in our beautiful state of Maine.”

Casey Cramton Photo courtesy of Dead River Co.

Cramton, a U.S. Army veteran and graduate of the Whittemore School of Business and Economics at the University of New Hampshire, will take over as president and CEO on July 1, the company said.

“I am certain Casey will bring a fresh perspective to the office, and under his leadership, Dead River Company will continue to serve our customers and our communities just as we always have,” Sherman said.