She suffered from dementia and had several months of deteriorating health until she “died peacefully, with family by her side” at her rural Georgia home of Plains, according to the Carter Center on Sunday.
In a statement, Carter added, “Rosalynn was my equal partner in everything I ever accomplished.”
“When I needed it, she provided me with sage advice and inspiration. Rosalynn’s presence in the world ensured that I always had love and support from someone.
Jimmy and Rosalynn Carter, who were married in 1946 at the ages of 21 and 18, were the longest-married presidential couple.
After his term ended in 1981, he also enjoyed more post-White House years than any president before him and she played an instrumental role during those years, including as part of the nonprofit Carter Center and the Habitat for Humanity charity.
She was seen as unassuming and quiet before coming to Washington in 1977 but developed into an eloquent speaker, campaigner and activist.
Her abiding passion, which carried far beyond her White House years, was for those living with mental illness, not because of any personal connection but because of a strong feeling that advocacy was needed.
Roslynn was little unknown outside of Georgia, where her husband had been a peanut farmer turned governor, prior to Jimmy Carter’s election as president in 1976.
A Democrat, he held office for just four years when Ronald Reagan, a former California governor and Hollywood star who was a Republican, defeated him in his 1980 attempt for reelection.
The president referred to her as “my closest adviser” and “an extension of myself” when describing the Carters as a team in Washington, DC. She was frequently asked to watch Cabinet sessions and talks on political strategy.
Carter claimed to have shared practically everything with his wife, with the exception of top-secret information, in a 1978 interview with magazine editors. He remarked, “I believe she has a deeper understanding of American culture and attitudes than I do.”
The first lady also was sent on important official missions to Latin America and was part of the unsuccessful campaign for ratification of the Equal Rights Amendment to the US Constitution to ensure equal treatment of women under the law.
Rosalynn Carter sought to support her husband by speaking in 112 cities in 34 states during a 44-day tour.
Though he lost handily to Reagan in the general election, Carter’s speeches and ventures into crowds were acknowledged for helping him defeat Democratic rival Ted Kennedy in the 1980 primaries.
She became interested in mental health concerns in the early 1970s after realizing how serious the issue was in Georgia and how reluctant people were to discuss it.
She served on a governor’s panel to enhance care for the mentally ill while she was Georgia’s first lady.