Rosalynn was the oldest of four children (two girls and two boys) born to Wilburn Edgar Smith, a mechanic and farmer, and his wife, Allie Murray Smith. Her father's death in 1940 at age 44, when Rosalynn was 13 years old, forced her to assume additional responsibilities and, as she would later say, ended her childhood.

In Plains, Georgia, where Rosalynn grew up and attended public schools, she met Jimmy Carter, the older brother of her best friend. While he was still a naval cadet and she was attending a local junior college, they became engaged. They married on July 7, 1946, at the Plains Methodist Church and began married life in Norfolk, Virginia, the first of several residences connected with his naval career. While raising three sons (born in 1947, 1950, and 1952), Rosalynn pursued her education, mostly through home study programs in literature and the arts. Their fourth child, Amy, was born in 1967.

In 1953, following the death of her father-in-law, Rosalynn reluctantly agreed to return to Plains, though she feared a loss of independence and fewer opportunities for travel. While Jimmy ran the family peanut business, she assisted him in bookkeeping, thus beginning a partnership that buoyed her confidence and increased his appreciation for her abilities. “I knew more about the books and more about the business on paper than Jimmy did,” she later wrote.

Her responsibilities increased after Jimmy won election to the Georgia Senate in 1962. Not only did she oversee the family business while he attended legislative sessions, she also handled much of his political correspondence and began to develop considerable respect for constituents' views. By the time Jimmy became governor in 1970, Rosalynn had gained the confidence to campaign on her own and began giving short, extemporaneous speeches, an activity that had terrified her earlier. Prompted by conversations with voters during the campaign, she took a strong interest in mental health issues. In the governor's mansion she presided over an establishment larger and more complicated than any she had ever managed, an excellent preparation, she later said, for the White House.

After Jimmy announced his candidacy for president, Rosalynn played an unprecedented early role. Eighteen months before the 1976 election, she began campaigning on her own, driving with a friend through towns where no one knew her to discuss why her husband should be president. Later she traveled by chartered plane to 42 states.

As first lady, Rosalynn participated in political affairs to an extent unmatched by any of her predecessors. She and her husband both acknowledged her status as a full working partner by scheduling weekly business lunches together, though her office remained in the East Wing, the traditional province of the president's wife. She attended cabinet meetings when the subject under discussion interested her and attracted attention for taking whatever seat was vacant, even if it happened to be the one normally occupied by Vice President Walter Mondale (Mondale, Walter). In June 1977 she visited seven nations in the Caribbean and Latin America and met with their leaders to discuss substantive matters related to defense and trade. Although she had prepared for the talks by studying Spanish and meeting with top economic and foreign policy advisers, she encountered considerable criticism, as well as some praise, on her return. Despite reports that she performed well, some critics questioned whether she should have assumed such a prominent role, given her lack of appointment or election. Thereafter she undertook no more such trips, though she did travel to various parts of the world for ceremonial occasions and on humanitarian missions, such as her 1979 trip to a refugee camp in Cambodia.

Like her husband, Rosalynn was noted for her practicality and her egalitarian attitudes. Her chief of staff earned the same salary as the president's chief of staff. The first lady showed relatively little interest in refurbishing the mansion, and she ordered no new china pattern to mark her stay. As a hostess she was criticized for her inexpensive menus and her refusal to serve hard liquor, a decision she defended by citing cost considerations. Her emphasis on economy was also reflected in her wardrobe: she showed little interest in “name” designers and wore the same gown to the 1977 inaugural ball that she had worn in Georgia when her husband became governor.

When Jimmy appointed members of the President's Commission on Mental Health in early 1977, he could not legally name Rosalynn as chair because of nepotism rules. However, she served as honorary chair and took an active role in the commission's work, which resulted in the submission of the Mental Health Systems Bill to Congress in May 1979. During debate on the bill, which passed in 1980, she testified before a Senate subcommittee, the first presidential wife to make such an appearance since Eleanor Roosevelt (Roosevelt, Eleanor) in 1945.

Rosalynn worked hard to reelect her husband in 1980 and bitterly resented his loss to Ronald Reagan (Reagan, Ronald W.). After leaving the White House at age 53, she directed her considerable energy to the same causes that had long interested her. She continued her efforts to improve mental health care and to promote other projects that, as she said, would result in “good for others.” Among these projects was Habitat for Humanity, a nonprofit organization that helped people to build their own homes. She also wrote several books, including First Lady from Plains (1984), which was widely praised as giving more insight into her husband's administration than most of the books by his top advisers.

Jimmy Carter sometimes pointed out that his wife's first name was Eleanor and that she had been as valuable a working partner to him as had Eleanor Roosevelt to her husband. Most Americans would agree, and Rosalynn's popularity was consistently high compared with that of other first ladies.