ORONO, Maine — Charles “Chick” “Charlie” John O’Leary Jr., the longtime head of Maine’s AFL-CIO and a University of Maine System trustee, died Friday at his home of lung cancer at the age of 76.

He was born Jan. 25, 1937, in Bangor, the son of Charles J. O’Leary and Doris Foley O’Leary.

A memorial service will be held 2 p.m. Wednesday, at the Unitarian Universalist Society of Bangor, 120 Park St.

O’Leary was head of the union for 20 years, from 1979 until his retirement in 1999. Those were difficult and turbulent times for the AFL-CIO and its members in Maine, many of whom worked in manufacturing jobs that were moved offshore.

“During the period of my presidency, the paper workers went from 17,000 production workers to about 7,000-8,000 today,” O’Leary said in an interview the Bangor Daily News published when he retired.

Much of that lost membership was replaced by state and other public employees who were allowed to unionize, he said.

“One of the toughest things for me was having to deal with plant shutdowns,” he said. “There are people who you know and work with on a regular basis — the production workers — and you have to go in and try everything in the world to try to save these mills.”

Former Gov. John Baldacci on Saturday called O’Leary “a very valued friend and confidant. He was just a great leader that we have lost.”

Baldacci said the O’Leary spent his entire career fighting for the working men and women of Maine to make sure they were able to make a living wage, had health care benefits, worked in a safe environment and were able to save for retirement. The former governor also said that university employees finally felt they had a voice on the board through O’Leary.

U.S. Rep. Mike Michaud, a former millworker whose political campaigns have been supported by union members, also mourned O’Leary.

“I’m forever grateful to have known and worked with Charlie,” Michaud said in a statement issued late Saturday. “He gained the confidence of people across Maine because he was committed to what he did, and he truly cared for the well-being of his fellow workers. The contributions he made to the advancement of workers’ rights here in our state are lasting and important.”

O’Leary was a childhood friend of Bill Cohen, a former U.S. senator and representative who went on to serve as Secretary of Defense under President Bill Clinton. The two grew up in the same Bangor neighborhood and played baseball together.

Decades later, O’Leary still referred to his friend as “Billy.”

After O’Leary announced his retirement from the AFL-CIO in early 1999, he told the Bangor Daily News during an interview that “Billy Cohen and I grew up on the same street. Now he gets to bomb Iraq and I don’t get to do anything fun.”

O’Leary also was well-known for his sense of humor, according to his obituary.

“He believed that humor was a necessary ingredient for life, and he lived by that mantra,” it said.

A favorite family story was “the day his wife came home to find him on the front lawn giving an interview to a local television crew about Boston Red Sox star Troy O’Leary, claiming with a straight face that Troy was his cousin,” the obituary said.

O’Leary attended John Bapst High School and started college at St. Michael’s College, then took a year off to work on an oil rig before completing his studies at the University of Maine, earning a master’s degree in history and government. He received a Fulbright grant to study at the American University in Beirut, Lebanon.

In 1968, O’Leary joined the labor movement, leading a statewide job-training program for the Maine AFL-CIO, according to his obituary. In 1972, he became director of the University of Maine Bureau of Labor Education. In 1978, he was elected president of the Maine AFL-CIO, a position he held until his retirement in 1998. He joined the University of Maine System board of trustees in 2005.

O’Leary is survived by his wife of 46 years, Pamela Braley O’Leary of Orono, his daughter Katie Ouellette and her husband, Ron, of Waterbury, Conn., his grandchildren, Alicia and Meagan O’Leary, whom he and his wife raised through their childhood, his daughter Ann O’Leary and her husband, Goodwin Liu, of Oakland, Calif., and grandchildren Violet and Emmett O’Leary–Liu. Also surviving are his sister and her husband, Doris and James Wentworth of Veazie, and his mother-in-law Arlene Braley.

In lieu of flowers, the family has asked that people consider making a donation in O’Leary’s name to the University of Maine Foundation, Two Alumni Office, Orono, ME 04473; or to Food AND Medicine, an organization started by laid-off workers and union members to support the basic needs of Maine families, located at Solidarity Center, 20 Ivers St., Brewer, ME 04412.