BLOOMINGTON — Russ Hagen was a seminarian working at a church on Bloomington's west side when he became acquainted with Lighthouse, the not-for-profit drug treatment program, as he helped a congregant addicted to amphetamines.

When he graduated from seminary, the head of Lighthouse asked Hagen if he was interested in working for the organization.

"I thought it would be an appropriate ministry," Hagen told The Pantagraph on Tuesday. "That was in 1974. It's been everything I hoped it would be and so much more."

Hagen, 68, of Bloomington, announced Tuesday that he was retiring, effective Jan. 7, from the organization, which became Chestnut Health Systems, after 43 years, including the past 36 as CEO.

When he joined Lighthouse, the drug treatment program had two dozen employees and a budget of $300,000. Today, Chestnut is a diversified health care organization with a $50 million annual budget and 700 employees across Illinois and beyond.

Hagen will continue to work part-time over the next two years, supporting Chestnut's global employee assistance program. Chestnut's board of directors will meet later this month to discuss succession plans.

"Russ has been a pioneer with behavioral health and addiction recovery services both in our community and internationally for many years," said Colleen Kannaday, president of Advocate BroMenn Medical Center in Normal.

"His visionary leadership at Chestnut has benefited many through the growth and expansion of services," Kannaday said.

"Russ Hagen is one of the most quietly impactful men in health care that I have known," said Dr. Paul Pedersen, vice president of medical affairs at OSF HealthCare St. Joseph Medical Center in Bloomington.

Chestnut, based at 1003 Martin Luther King Drive, Bloomington, is experiencing is second executive change in recent months.

In June, Chief Operating Officer Alan Sender, 63, announced his retirement, effective July 7, after 29 years with Chestnut. He remains a part-time consultant.

But Sender and Hagen said both retirements had been in the works for several years and the timing had been coordinated.

"In the last two years, we have been training and mentoring younger leadership who have been assuming more responsibilities," Hagen said. "I'm confident in the sustainability of the organization in the future."

Chestnut has 256 employees in Bloomington-Normal, 417 in the Metro East area and 37 at other locations.

Chestnut's lines of business are substance abuse treatment for adults and adolescents, mental health treatment, substance abuse research and training, employee assistance programs for U.S.-based and multinational companies,  mental health stabilization, substance use detoxification, consumer credit counseling and primary health care through federally qualified health centers on Chestnut Street in Bloomington and in Granite City.

"Chestnut has grown primarily because we always stayed in touch with the communities we serve," Hagen said. As Chestnut helped to identify community needs — such as adolescent substance abuse treatment, mental health treatment, employee assistance programs and substance abuse research — the organization sought partners and responded.

"Russ Hagen," Sender said, "is the essence of collaboration."

Follow Paul Swiech on Twitter: @pg_swiech