William G. Milliken, a moderate Republican who as governor led Michigan through a period of profound transformation in the 1970s, as it went from being an economically scarred industrial state to one that embraced technology, business diversity and environmental quality, died on Friday at his home in Traverse City, Mich. He was 97.

His son and only immediate survivor, Bill Jr., confirmed the death.

Mr. Milliken was the longest-serving governor in Michigan’s history, a 14-year tenure that began in January 1969, when, as the state’s lieutenant governor, he succeeded George Romney, who had left office in the middle of his term to join President Richard M. Nixon’s cabinet. Mr. Milliken went on to be elected to three full four-year terms.

Days before he became governor in 1969, he told a joint legislative session, “It is my greatest hope that this administration will be known for its compassion, its idealism, its candor, and its toughness in the pursuit of public ends.”

That vision was largely borne out. His administration invested in urban housing and education, defended auto industry jobs and profits in the wake of the 1973-74 Arab oil embargo, strengthened higher education and put innovative environmental protections in place.