He was known as a brilliant lawyer, a dynamic and brash speaker and an innovative governor. His accomplishments included saving rail service for much of the state, cutting property taxes and leading the nation in connecting classrooms to the Internet.
Janklow also had a reputation as an abrasive man who refused to compromise and sometimes blasted his opponents in public. Yet he quietly helped many people who were down on their luck, paying to send young people to college or buying gear for a baseball team from a Native American reservation.
"My whole life has been fighting for people. It's what I know how to do in terms of representing people," Janklow said shortly before his political career ended.
His habit for speeding was well-documented. Between 1990 and 1994 he received a dozen speeding tickets.
In August 2003, he sped through a stop sign on a rural road, striking and killing motorcyclist Randolph E. Scott, a 55-year-old Minnesota farmer. Janklow was convicted of second-degree manslaughter, reckless driving and two other charges. He served 100 days in prison.
"I understand. I killed somebody," Janklow quietly told the judge during sentencing. "I can't be punished more than I'm punishing myself."
William J. Janklow was born Sept. 13, 1939, in Chicago and moved with his mother to her hometown, Flandreau, S.D., after his father died.
A troublemaker in high school, Janklow dropped out to join the Marines. He later enrolled in the University of South Dakota and received a law degree in 1966.
In 1960, he married Mary Dean, and they raised three children.
After Janklow represented poor clients on the Rosebud Sioux Indian Reservation from 1966 to 1973, the state hired him to prosecute members of the American Indian Movement for a riot at the Custer County Courthouse.
He had to defeat his boss to be elected attorney general in 1974, then went on to run for governor.
"If I had to do it over, I'd do everything I did, but I'd stop at a stop sign," Janklow said in November when he announced he had brain cancer.