If you want to walk across the country, you need a few things: passion, persistence, and good shoes.

Luckily, 90-year-old Opal Lee has all three.

Lee set out on foot from her home in Fort Worth, Texas, on Aug. 31, 2016, with a mission to walk all the way to Washington D.C. And no, it's not just for exercise, a Guinness record, or some sort of Forest Gump-level brush with boredom.

Lee is driven by something much bigger: purpose.

Lee's purpose goes back to a day called Juneteenth.

In 1865, two and a half years after President Lincoln signed the Emancipation Proclamation and months after General Lee surrendered at Appomattox, Major General Gordon Granger and Union soldiers arrived in Galveston, Texas, with the news that all slaves were officially free.

He delivered the announcement on June 19, 1865 (June + Nineteenth), and Juneteenth began.

Today, many people celebrate the holiday individually with barbecues and backyard parties. But Opal Lee would like to see it turn into a day of service, similar to Martin Luther King Jr. Day — complete with job fairs, educational opportunities, and support for victims of abuse.

"It just can't be the frivolity that people think of it as," she said. "We have an opportunity to help."

That's why Lee is walking all the way to Washington, D.C. — to hand deliver a petition to President Obama about making Juneteenth a National Day of Observance.

She's been working with her local Juneteenth organization for the past 40 years. Her local organization has appealed to Congress and previous presidents over and over again, hoping to take the event national.

So far, nothing has caught the White House's attention, which is why Lee's taking a different tactic this time around.

"I thought, if a 90-year-old got out there walking toward Washington, D.C., from Fort Worth, Texas, somebody would take notice," she said. "And maybe they would decide they wouldn't want that little old lady dying on their watch, and they'd invite me up there so I could tell 'em what I've got on my mind."

Lee won’t walk all 1,400 miles from Fort Worth to Washington, D.C, but she will walk most of them.

Rain or shine, she typically walks two miles in the morning and two in the afternoon every day. She jumps to different cities along the route, including Texarkana, Shreveport, and St. Louis, welcomed by by churches, schools, NAACP chapters, and anyone else who will have her.

Each day, she dons a reflective vest and her sturdy walking shoes.

And she sets out, sign in hand, to take on the day's mileage.

Strangers, local groups, and churches have organized around her, some honking and cheering from their cars.

Some even join her for a mile or two.

"The support has been fantastic," she said. "I actually have fun doing this."

At the end of each day, Lee often stops to talk to school kids, locals, and anyone curious about Juneteenth.

She also talks about her walk before gearing up for the next mile in the next city.

It's not a pursuit for the faint of heart, but Lee is not familiar with the phrase "give up."

Like Opal Lee herself, Juneteenth is uniquely American, rooted in strength and history.

A majority of states have already made Juneteenth (also called Emancipation Day) a holiday at the state level, on equal footing with "Will Rogers Day" in Oklahoma or "Confederate Memorial Day" in South Carolina.  

This day is not just a "black holiday," it's a celebration of gratitude and freedom.

It's a lasting reminder of how far we've come as a nation and how far we've yet to go.

"It should be our way to thank the people who were responsible for our deliverance. The slaves didn't deliver themselves," Lee said. "There were Quakers and Jews and abolitionists and the Underground Railroad — all kinds of people who worked untiringly to help slaves get free, and we need to be aware of that and make others aware of that."

So that's why Mrs. Lee walks: for progress and for a better America.

With courage, heart, and one foot in front of the other, she will get to D.C.

You can help Lee along the way by following her journey on Facebook or her website. And if you're on #TeamOpal, be sure to  read and sign her official White House petition too. The first petition expired before it reached the necessary 100,000 signatures, but again, giving up is not something Opal Lee does. Ever.

After all, she's just keeping the movement going until the next generation steps up.

"I'm optimistic that somewhere along the line, the young people are gonna take the reigns and they're gonna do a lot better than I've done over the years," Lee said

Those are big, sturdy shoes to fill. But we owe it to her and generations of Americans to give it our best shot.