In the aftermath of the assassination of John F. Kennedy, Lyndon B. Johnson took the Oath of Office, inheriting a country in mourning, a country in war, and a country in the midst of the civil rights movement. By his side through it all, his wife, Lady Birde Johnson, and in a new ABC News studios documentary, The Lady Birde Diaries, we hear her narrate her own life. Let's take a listen.

It all began so beautifully. Lyndon Johnson and Mrs. Johnson have just arrived. Lyndon and I road down the avenue in one car. Suddenly, there was a shot. I've heard the words, the President is dead.

And we are joined now by Director Dawn Porter. Dawn, thank you so much for coming back on the show. Just a remarkable set of recordings giving us new perspective into that time from her personal vantage point. You had to go through more than 123 hours of recordings. So what were you thinking about? What moved you as you were listening?

I had done films about Bobby Kennedy. I'd done films about Don Lewis. And so I was really familiar with this time period, but it was really extraordinary to hear her first-person recounting of the things that she saw. This was the period of Vietnam. Martin Luther King Jr. Was assassinated. Bobby Kennedy was assassinated. So much turmoil was happening in the country. And she was recording every day, as you said, 123 hours of audio tapes.

And it's clear that she's passionate about these issues. How much of a role did she actually play?

That was one of the great discoveries of this film, is that Lady Bird actually was incredibly instrumental in working with her husband on his policy decisions. One thing that people don't remember is that there was no plan of succession in the United States. So when Kennedy was assassinated, Johnson had no Vice President. That plan of succession actually happened as a result of Kennedy's assassination. The Congress realized we needed to have a plan in case the President was assassinated and the Vice President had to step up. So for that first year and a half of his being in office as President, Lynden Johnson had a real kitchen cabinet, and Lady Jipber Johnson was definitely instrumentally part.

Of that. What we learned from the tapes is about some of the personal tolls of the presidency.

Another extraordinary moment that we found is Lynden Johnson suffered from extreme depression, and Lady Bird recounts this. I think that's probably part of the reason that she asked that the tapes be embarked until after her death. But Lynden Johnson, more than one time, thought that he might resign the presidency. And one time in particular, he was about to give an address to the nation, and Lady Bird writes out his resignation speech, and he takes it and he puts it in his pocket. And no one knows, there's only three people who know that this is possibly going to happen, that maybe Lyndon Johnson is going to resign the presidency during the State of the Union. And so Lady Bird is recording, and we found the footage of the speech, and she says, Is he going to do it? Is he going to reach into his pocket? And when you see the footage, you see that moment where he hesitates, and then he doesn't.

What do you like people to take away from this film?

I'd like people to understand that she did far more than plant some flowers. That is what she is known for. In fact, she's an environmentalist. Ladybird's research led to more than 300 environmental bills being passed during the Johnson administration. It also is the foundation for the EPA. Richard Nixon invites Ladybird to the signing of the legislation establishing the EPA. I think in this day and age we are still trying to figure out what is the right role, what is the acceptable role for the first lady. Dr. Jill Biden is the first first lady, we've had who is outside paid work. And so I really was thinking a lot about we still have a long way to go in terms of people accepting women in public, in political life.

Dawn Porter, always fascinating topics that you're bringing to life. We so appreciate it. The Ladybird Diaries is now streaming on Hulu.

Hi, everyone. George Stephanopoulos here. Thanks for checking out the ABC News YouTube channel. If you'd like to get more videos, show highlights and watch live event coverage, click on the right over here to subscribe to our channel. And don't forget to download the ABC News app for breaking news alerts. Thanks for watching.