Former University of Montana President George Dennison died Tuesday morning from complications of non-Hodgkins lymphoma, according to the university.

Dennison, who grew up in the Flathead Valley, was the longest-serving UM president. He was 81.

He retired in 2010 after leading the university for 20 years.

“He was an exceptional leader,” said George Ostrom, a longtime Flathead radio personality and newspaper columnist. “He brought great progress to UM. The university made great strides under his leadership.”

Ostrom served on UM President’s Citizen Advisory Council during Dennison’s tenure. He and Dennison also grew up together as “miners’ kids” because both of their fathers worked at the Flathead mine near Kila.

“He was very personable and very smart,” Ostrom added.

Dennison grew up in the Kila area and graduated from Flathead County High School in 1953. He served in the U.S. Navy from 1953 to 1957.

He received a bachelor’s degree from UM in 1962, a master’s in 1963 and a doctorate in history from the University of Washington in 1967. He came to UM from Western Michigan University, where he served as the provost and vice president for academic affairs from 1987 to 1990. Prior to that he spent 18 years at Colorado State University, where he was a history professor and served in several administrative positions.

Dennison married Kalispell native Jane Schroeder in 1954, and their 62-year union produced two sons: Robert, a retired teacher and coach in Tecomseh, Kansas, now working in information technology, and Rick, the offensive coordinator for the Denver Broncos.