The trail stretches from Georgia to Maine, and if Pappy completes all of it, he will be the oldest person to ever hike it.
Pappy, as he's known on the trails, has already hiked more than 1,000 miles of the Appalachian Trail, starting in Georgia this March and hiking up to Virginia.
Instead of finishing in Maine with Mount Katahdin, Pappy is doing the hike out of order, so that he could conquer Katahdin in milder weather.
Pappy has always been active, and completed the Appalachian Trail before in 1996, when he was 65 years old. He has also completed the Pacific Crest Trail, the Continental Divide Trail, and rode his bicycle around the perimeter of the United States.
"I just have the desire to be fit," said Pappy. "They also say that a moving target is difficult to hit."
This time he is hiking it with his daughter Vikki Kubilius Fortier, who called her father her best friend.
"I've seen so much and done so much that I probably wouldn't have done if I wasn't accompanying him," she said fondly.
They said hiking Katahdin was harder this time. They had to stay on the mountain overnight, but they made it.
"The wind was blowing and we couldn't sleep, we shivered most of the night," said Pappy.
Pappy now lives in South Carolina, but was born in Lithuania and came to the United States after World War II. He lived in Germany for a time in a displaced persons camp while he arranged passage to the US.
He spoke fondly of his time in the army, where he served as a linguist.
"I live in the best country in the world," said Pappy. "Look what it did for me, I was homeless living in foreign country...and then when I came to the United States, things changed."
That positive spirit has helped Pappy in some scary moments, like one bear encounter.
"I open a can of sardines and I'm eating, and I see two bears," said Pappy. "They stood up on their hind legs and they're smelling my sardines. So I backed up and took off."
Pappy said one of the best parts of hiking is seeing so much of the country he loves, and the people you meet along the way.
"You ask a Mainer a direction, and he'll say you can't get there from here," joked Pappy.
It's hard to describe a man who has seen and done so much, but he says it's all quite simple.
"Don't just stay home and do hardly anything, be active," said Pappy.
He has about 1,000 miles left before he completes the Appalachian Trail.
Once back home in Myrtle Beach, Pappy said he'll take it easy, and focus on his hobbies like photography and ballroom dancing.