Plains, Georgia – Former first lady Rosalynn Carter, the wife of former president Jimmy Carter, died Sunday at age 96 at the couple's home in Georgia, their nonprofit organization announced.

Carter was best known for her work post-White House, as she and her husband championed human rights, democracy, and health issues around the world – all while maintaining a notably humble public image.

She had joined her husband in at-home hospice care on Friday after being diagnosed with dementia in May.

"Former first lady Rosalynn Carter, a passionate champion of mental health, caregiving and women's rights, passed away Sunday... at her home in Plains, Georgia, at the age of 96," the Carter Center said in a statement.

"She died peacefully, with family by her side."

"Rosalynn was my equal partner in everything I ever accomplished," Jimmy Carter said in the statement.

"She gave me wise guidance and encouragement when I needed it. As long as Rosalynn was in the world, I always knew somebody loved and supported me," the former Democratic president said.

Throughout Jimmy Carter's long political career, his wife was at the heart of his campaigns. Once in the White House – from 1977 to 1981 – Rosalynn Carter stood out as a first lady intent on being involved in policy.

"She attended Cabinet meetings and major briefings, frequently represented the Chief Executive at ceremonial occasions and served as the president's personal emissary to Latin American countries," according to the White House website.

Rosalynn Carter was born in the small town of Plains on August 18, 1927, as the first of four children. At 13 her father died and she worked alongside her mother, who became a dressmaker to make ends meet.

She met Jimmy Carter in 1945 while she was in college and he was on leave from the US Naval Academy in Annapolis.

They married in 1946, and hold several longevity records in US politics: the longest-wed presidential couple and, for 99-year-old Jimmy Carter, the oldest living US president.

According to the Carter Center, the former first lady is survived by her four children, 11 grandchildren and 14 great-grandchildren, after losing a grandson in 2015.

"Besides being a loving mother and extraordinary first lady, my mother was a great humanitarian in her own right," the Carters' son Chip Carter said in the Center's statement.

"She will be sorely missed not only by our family but by the many people who have better mental health care and access to resources for caregiving today."

The family announced in February this year that Jimmy Carter had entered hospice care in Plains – at the same modest house he and Rosalynn have lived in since the 1960s.

The one-term Democratic president has since surprised many by continuing to welcome visitors, receive news about the Carter Center's humanitarian work, and frequently enjoy ice cream, according to his family.