US President Joe Biden, first lady Jill Biden and a host of their predecessors joined mourners in Atlanta, Georgia, on Tuesday to pay tribute to former first lady Rosalynn Carter, who died on November 19, aged 96.
Ms Carter was diagnosed with dementia in May and died shortly after entering hospice care.
Her husband, former president Jimmy Carter, who has been in hospice care at their home in Georgia, attended the service, which took place at Glenn Memorial United Methodist Church.
All five living first ladies sat in the front row.
Vice President Kamala Harris and former president Bill Clinton were among those to pay their respects.
Country music stars Garth Brooks and Trisha Yearwood performed a rendition of John Lennon’s Imagine.
“Mum was always well-informed on the issues of the day,” the Carters' son James Earl “Chip” Carter III told the service, describing her “partnership” with Mr Carter during his presidency.
“In the White House, mum asked so many questions that he finally said that she should attend cabinet meetings. So she did and caught a lot of flak for that.”
Her children and grandchildren recalled fly-fishing trips with Rosalynn Carter and her fondness for using mayonnaise in her recipes, and how her human warmth guided her public service, Reuters reported.
The Carters were the longest-married presidential couple, having been married for 77 years. The former first lady was considered one of Mr Carter's closest advisers during his presidential term.
“Rosalynn was my equal partner in everything I ever accomplished. She gave me wise guidance and encouragement when I needed it,” Mr Carter said in a statement after his wife's death.
“As long as Rosalynn was in the world, I always knew somebody loved and supported me.”
Ms Carter was also a fierce advocate for mental health and was part of a commission during Mr Carter's presidential term that would result in the 1980 passage of the Mental Health Systems Act.
After leaving the White House, the couple established the Carter Centre in Atlanta, which supports human rights and democracy.
The Bidens, who praised Ms Carter's legacy on her death, met privately with Mr Carter and expressed their condolences, the White House confirmed.
"The President and the first lady shared a private moment with President Carter before the ceremony, and were able to express their condolences directly to the Carter family," White House Press Secretary Karine Jean-Pierre said on Tuesday evening.
Mr Biden has shared a long friendship with Mr Carter that dates back to the outset of their national political careers, Bloomberg reported. In 1976, Mr Biden was the first elected official outside Georgia to endorse Mr Carter’s presidential campaign.
They kept a close bond over decades. Three months after entering the White House, the Bidens visited the Carters at their home in Plains, Georgia.