WATERVILLE — George Spann, 23-year president of Thomas College and the man credited with revitalizing the school, announced Monday that he will retire in June.

He said he plans to spend more time with his grandchildren and do volunteer work.

Spann, who was unavailable Monday, provided comments via Jennifer Buker, Thomas College director of public relations.

Spann said he’ll retire wishing that Thomas was more widely known outside of Maine. He said his fondest memories at Thomas revolved around the thousands of students he met during his two-plus decades and that his biggest success was that “the college is still here and thriving.”

Two members of the Board of Trustees credited Spann, 68, with revitalizing the institution founded in 1894.

Thomas graduate Conrad Ayotte called Spann’s arrival in 1989 at the liberal arts and business college a watershed moment and said the school community owes Spann “an enormous measure of gratitude for all that he has done to prepare that future.”

Ayotte, co-chairman of the board, said Spann was the right man at the right time for Thomas.

“George took on a small struggling school, and made it into what it is today — a strong, vibrant college poised for significant growth and a tremendous future,” Ayotte said in a news release.

Graduate and board co-chairman Todd Smith said it would be difficult to overemphasize Spann’s leadership and impact.

“Because of his hard work and the tremendous foundation he has laid, this time of transition will be smooth and the college’s plans will continue to progress,” said Smith, also in a news release.

While the 1980s at Thomas were marked by a downturn in enrollment as well as financial challenges, the college news release said Spann, together with Thomas’ board of trustees and administration, controlled costs and reinvigorated student recruitment and retention.

Those successes led to the renovation and expansion of the campus, a broadening and strengthening of academic programming and a new era of philanthropic fundraising for Thomas, according to the release.

According to the college website, 94 percent of the 700 Thomas students receive financial aid. One year at the institution costs $31,940.

In January, Thomas unveiled plans for a dozen new buildings, including five residence halls and a library, plus a near-doubling of the campus to include new athletic fields.

Faced with growing student enrollment and a need for more building space, college officials said in January that they sought to transform the campus while maintaining its intimate feeling.

As of the end of the 2010 fiscal year, Thomas’ endowment was $6.5 million.

In 1999, Thomas launched its guaranteed job placement program, which promised that graduates who are not employed within six months after they graduate can return to Thomas for two more years, tuition-free, or that Thomas will pay their monthly student loans for one year or until they land their first job.

For many years before to taking the position, Spann and his wife, Marty, vacationed in Maine. She died Sept. 13 at 65, after a 12-year battle with breast cancer.

Spann said another college president had encouraged him to apply for the Thomas post.

“He loves Maine,” said Buker.

Before arriving at Thomas, Spann taught modern British history and modern European history at the University of Pennsylvania and Rutgers University in New Jersey. He also worked for a publishing company and had a variety of college administrative positions, according to the college website.

In 1974, Spann earned a doctorate in history from the University of Pennsylvania. The Swarthmore College graduate is also a graduate of Harvard University’s Institute for Educational Management.

It was at Swarthmore that he met his then wife-to-be, Marty. They married in 1966. The Spanns have an adult son and daughter, Geoffrey and Jennifer.

The American Cancer Society’s Relay for Life held in October at Thomas was dedicated to Marty’s memory and the Relay for Life of Waterville, held annually at Thomas, was re-named Relay for Life of Waterville In Memory of Martha “Marty” Spann.

In addition to his work at Thomas, Spann, who lives in Belgrade, is a director of the Waterville Development Corporation, a director of the Maine Children’s Trust, a Rotarian and a member of the Waterville Regional Arts and Community Center.

Plans to honor Spann for his 23 years of service will be forthcoming, said Buker.

The college will undergo a nationwide search for its next president.