As the sombre ceremony began and a bitterly cold wind blew, Jimmy Carter's flag-draped coffin was carried up the stone steps of the cathedral by a military honour guard.
Mr Carter had reached the age of 100 when he died on December 29, 2024.
In the two days leading up to the funeral, tens of thousands of people filed through the US Capitol building to pay their respects to Carter, who was president from 1977 to 1981.
Fellow Democratic President Joe Biden began his eulogy of the 39th President by recalling how their relationship started, by Mr Biden endorsing the Georgian ahead of the 1976 presidential campaign.
Mr Biden says the former president taught him the importance of treating everyone with dignity and respect.
"Jimmy Carter's friendship taught me - and through his life - taught me the strength of character is more than title or the power we hold. It's a strength to understand that everyone should be treated with dignity. Respect that everyone, and I mean everyone, deserves an even shot, not a guarantee, but just a shot."
Burdened by an ailing economy and the Iran hostage crisis, many mourners hailed him as an example of decency and humility for today's breed of highly partisan politicians.
Republican president-elect Donald Trump, who will return to office on January 20, was among the luminaries at the funeral.
Mr Trump sat next to former president Barack Obama, whispering a greeting in his ear.
To Mr Obama's right were Laura and George W Bush; and Hillary and Bill Clinton.
Mr Biden and first lady Jill Biden took their seats in the first row next to Vice President Kamala Harris and second gentleman Douglas Emhoff.
Mr Carter lived so long that two of the eulogies were written by people who died before him — his vice president Walter Mondale and his White House predecessor Republican Gerald Ford.
Mr Carter defeated Mr Ford in 1976 but the presidents and their wives became close life-long friends.
And it was Steve Ford, Gerald Ford's son, who read the eulogy remarks written by his father years before at Mr Carter's funeral.
"By fate of a brief season, Jimmy Carter and I were rivals, but for the many wonderful years that followed, friendship bonded us as no two presidents since John Adams and Thomas Jefferson. Now, this is not to say that Jimmy never got under my skin. But has there ever been a group of politicians that didn't do that to one another? During our 1976 contest, Jimmy knew my political vulnerabilities and he successfully pointed them out. Now, I didn't like it, but little could I know that the outcome of that 1976 election would bring about one of my deepest and most enduring friendships."
Carter was born a peanut farmer in Plains, Georgia and served as that state's governor from 1971 to 1975.
He was awarded the Nobel Peace Prize in 2002 for his humanitarian work.
One of his grandsons, Jason Carter, who serves as chair of the Carter Center Board of Trustees, says the man he called "Paw-paw" and his grandmother Rosalynn Carter, who died in 2023, remained humble and true to their values, choosing to remain in their modest home in Plains.
"They were small town people who never forgot who they were and where they were from. No matter what happened in their lives. But I recognise that we are not here because he was just a regular guy. As you've heard from the other speakers, his political life and his presidency for me was not just ahead of its time. It was prophetic. He had the courage and strength to stick to his principles, even when they were politically unpopular. As governor of Georgia half a century ago, he preached an end to racial discrimination and an end to mass incarceration. As president in the 1970s, as you've heard, he protected more land than any other president in history."
The ceremony concludes six days of national rites that began in Plains, Georgia, where Carter was born in 1924, lived most of his life and died after 22 months in hospice care.
Ceremonies continued in Atlanta and Washington, where Carter, has lain in state since Tuesday.
