Gardner died Friday in his Tacoma home, The Seattle Times reported.
Gardner was known for his work in education, the environment, social issues and healthcare, the Times said.
Under his tenure, the state instituted required standardized tests for high school students, as well as a program for low-income pregnant women.
Booth started out in politics in 1970 when he won a state Senate seat, and later become a Pierce County executive in 1981.
He won the governor race in 1984 after overcoming a lack of statewide name recognition, the Times said.
After his two terms as governor, President Bill Clinton appointed him a deputy U.S. trade representative,and he later headed the "assisted death" initiative in 2006.
In 2008, the state passed the nation's second law allowing doctors to help terminally ill patients die, the Times reported.