JOHN YANG: Good evening.

I'm John Yang.

Former First Lady Rosalynn Carter has died at the Carter's home in Plains Georgia.

In May, Mrs. Carter disclose she had been diagnosed with dementia.

And just Friday it was announced that she had moved into hospice care alongside former President Jimmy Carter, her husband of 77 years.

And the statement tonight Mr. Carter said his wife was his equal partner in everything he ever accomplished.

Judy Woodruff covered the Carters both in Georgia and in the White House and she has this remembrance.

JUDY WOODRUFF (voice-over): Whether she was fighting disease in a foreign land, serving at the White House, or enjoying home in Plains, Georgia, Rosalynn Carter led a life of advocacy.

She reflected on it all in 2014.

At a forum in Grand Rapids, Michigan.

ROSALYNN CARTER, Former U.S. First Lady: This though much first lady can do, and I don't think -- I don't think they'll ever be another first lady who just posed it and it's access hostess in the wild as some in the past have done.

JUDY WOODRUFF (voice-over): Born Eleanor Rosalynn Smith.

She was the daughter of an auto mechanic and a dressmaker.

She grew up next door to the Carters in Plains, Georgia, and eventually married the future president in 1946.

ROSALYNN CARTER: The day we got married, I thought, we're going to have an adventure some happy life.

It turned out my life with Jimmy Carter has been more adventurous than I ever dreamed it would be.

JUDY WOODRUFF (voice-over): The couple had three sons and a daughter, Amy, who became the first young child to live at the White House since the Kennedy years.

Before starting his road to Washington, Jimmy Carter served in the Navy, ran a Peanut Farm, spent four years as a state senator, and follow that with a term as governor of Georgia.

Then came the race for the Democratic presidential nomination.

1976.

ROSALYNN CARTER: People asked me everyday how can you stand for your husband to be in politics, and everybody know everything you do?

And I just tell them that we were born and raised.

I still live in Plains, Georgia.

It has a population of 683.

And everybody has always known everything.

JUDY WOODRUFF (voice-over): The Carter's claimed the nomination at the Democratic National Convention that July.

And as the phone campaign geared up, Mrs. Carter sat down with Jim Lehrer and Robin McNeil making the case for her husband.

ROSALYNN CARTER: When you scrimp and save like we did to build up a business and then get into government.

It's unbelievable the ways and extravagance.

That's what I think that Jimmy can cut out.

And the reason I think he can do it, and this is what I hope the American people will understand is that he has no obligations.

It's the first time that we have had a chance to elect a president with no strings attached.

You can just do exactly what's right for the people.

JUDY WOODRUFF (voice-over): That November, Jimmy Carter narrowly defeated Republican incumbent Gerald Ford, who would become president when Richard Nixon resigned.

JIMMY CARTER, Former U.S. President: I, Jimmy Carter, do solemnly swear -- JUDY WOODRUFF (voice-over): Two months later, the nation's 39th President was sworn in with Rosalynn by his side.

The new First Lady became a leading advocate for the mentally ill, as Honorary Chair of the President's Commission on Mental Health.

She also served as one of her husband's closest advisors, at times representing him in meetings with foreign dignitaries, and often sitting in on cabinet meetings.

And she recalled in that 2014 forum.

ROSALYNN CARTER: Because I had campaigned, I knew all the issues.

I had told people I was going to, you know, work on issues.

And I was doing -- I was traveling out in the countryside having press conferences, so I had to know what was going on.

And so, one day in February, he said, why don't you come to the cabinet meetings, and you will know why we do things.

Well, that was a great invitation.

I went every time I didn't have a conflict, and I tried not to have conflicts.

JUDY WOODRUFF (voice-over): But the Carter Presidency was marred by the Iran hostage crisis and a stagnant economy with double digit inflation.

And that paved the way for a landslide last a Republican Ronald Reagan in 1980.

Still though they left Washington, they continue their advocacy through the Carter Center in Atlanta.

Mrs. Carter discussed its inception with the NewsHour, Charlayne Hunter Gault in 1995.

ROSALYNN CARTER: You realize when you leave the White House, that you still have the resources, anybody in the world will help you with anything if you ask them.

Any expert on any issue will help you with anything because Jimmy was president.

What do you do with that?

I mean, we pondered that a lot.

And then the Carter Center really developed even beyond our wildest expectations.

JIMMY CARTER: So this is a magic net.

JUDY WOODRUFF (voice-over): The center gained renowned for bringing humanitarian aid in fighting disease, including the parasitic guinea worm in remote impoverished parts of the world.

The couple also traveled the globe trying to resolve international conflicts, as well as monitoring national elections in three dozen countries over the years.

And starting in 1984, they volunteered with Habitat for Humanity to build homes for needy families, both in the U.S. and in more than a dozen foreign countries.

Along the way, the former first lady pursued her own longtime interests, especially mental health.

ROSALYNN CARTER: Mental illnesses can be diagnosed, they can be treated effectively.

And the overwhelming majority can lead normal lives living at home working, going to school.

And it's just a tragedy when people suffer, and they'll get help.

JUDY WOODRUFF (voice-over): In 2015, when the former president announced he had cancer, he paid tribute to the woman he shared his life with.

JIMMY CARTER: The best thing I ever did was married and Rosalynn.

That's the pinnacle of my life, and we've had 69 years together.

And so that's the best thing that happened to me.

JUDY WOODRUFF (voice-over): Through it all, they always stayed connected to planes were Rosalynn Carter remained active in her own community until the end of her life.

JOHN YANG: Rosalynn Carter was 96 years old.