Guy Jennison was the grandson of Chief James Wind, son of Catherine Jennison, and a central figure in mid-twentieth-century Ottawa leadership. He joined the tribal council in 1912, and he became chief after the illness and death of Manford Pooler in 1930. Jennison held the position of chief for over thirty years, and he guided the Ottawa Tribe through major political changes.

In 1938, Jennison led the Ottawas to adopt a tribal constitution under the Thomas-Rogers Act. He also entered public service as an Ottawa County Commissioner from 1940 to 1946 as a Republican. During the late 1940s, Jennison initiated Ottawa claims before the Indian Claims Commission, and these efforts led to tribal members receiving compensation for past treaty violations.

The 1950s brought new challenges and political shifts. The Bureau of Indian Affairs increasingly withdrew services for Ottawa people, but federal officials still supervised and controlled tribal affairs. Receiving few benefits from federal recognition, Jennison saw the new policy of termination as a means to escape federal paternalism. The BIA also made false promises of quick claim settlements and new educational benefits if the Ottawa agreed to terminate.

In 1956, Jennison endorsed the termination of federal supervision, and the Business Committee joined him in supporting termination legislation. The majority of Ottawa citizens did not get a vote on the termination proposal. After Congress passed the termination act, Jennison led the Ottawa Tribe reorganize under a state charter in 1959.