Milliken, who spent 14 years as first lady, died on Friday morning at her family's home in Traverse City, her son, William "Bill" Milliken Jr., said. She had been diagnosed with ovarian cancer, he said, and was receiving hospice care.
Early in her husband's political career, she dutifully played the role of an unassuming and supportive spouse. But she evolved into an outspoken advocate of issues close to her heart during her record 14 years as Michigan first lady.
She criticized highway billboards as unsightly clutter shortly after her husband, Republican William Milliken, became governor in 1969, drawing the wrath of the outdoor advertising industry. At her urging, her husband hiked the Pigeon River State Forest — after which he decided to limit oil and gas development in the scenic northern Michigan forest.
It was the couple's daughter Elaine, a lawyer and feminist, who died of cancer in 1993, who influenced her mother to take a stand for women's equality. Helen Milliken did so, vigorously campaigning for abortion rights and the ill-fated Equal Rights Amendment, which stated equality of rights "shall not be denied or abridged by the United States or by any state on account of sex."
Even into her 80s, she remained active in community affairs and as an environmentalist. Milliken helped organize a foreign policy lecture series at Northwest Michigan College and took a course on the life of Mozart.
She told The Associated Press in 2006 about her concerns that many younger women were shying away from political activism and the "feminist" label.
"They don't know their history," she said at the time. "Young women take so much for granted now."
Feminism, she said, had "been redefined and misinterpreted" by conservatives as wild-eyed radicalism.
"Nobody ever saw anybody burn a bra; they're too expensive," she said. "But the myth has survived. There have been excesses, but the goal has always remained the same: equal opportunity for women."
The former Helen Wallbank, daughter of a Denver-area attorney, earned a bachelor's degree from Smith College in 1945, and met William Grawn Milliken as he underwent military training in Colorado during World War II.
After marrying, they settled in his Michigan hometown of Traverse City, which also was home to the family-owned Milliken Department Store.
William Milliken was elected to the state Senate in 1960, following in the footsteps of his father and grandfather, both Republican state senators. Shortly afterward, Milliken and other moderates rebelled against the right-wing leadership, issuing a manifesto with progressive stands on issues such as taxes and civil rights.
Elected lieutenant governor in 1964 and 1968, Milliken succeeded fellow Republican George Romney as governor in January 1969 when Romney joined President Richard Nixon's Cabinet. Milliken won the election that fall and was re-elected twice, but decided not to seek a fourth term in 1982. He retired from politics unbeaten at age 59.
His wife, however, wasn't done with politics.
Helen Milliken continued to be a sought-after political commodity long after her husband's retirement. In 1994, she was even asked to be the running mate of Democratic gubernatorial candidate Howard Wolpe as he sought to boost his underdog campaign against Republican Gov. John Engler.
She declined, later telling the AP "it just didn't seem like the right move to make at the time."
Milliken is survived by her husband and her son, William Jr.
— Associated Press writers David Runk in Detroit and John Flesher in Traverse City contributed to this report.