About a month ago, Chris Brannigan started his trip in Maine and made his way to Philadelphia on Thursday.
He has nearly 500 miles to go until he reaches his destination of Jacksonville, North Carolina.
"I'm doing the whole journey barefoot," Brannigan said. "I don't enjoy walking barefoot. I'm not an athlete. I'm not some kind of endurance junkie, 'm really just doing this because it's a way to get people to focus on this issue and hopefully help us raise the money we need."
Currently serving in the British Army, Brannigan said his goal right now is to help kids like his 9-year-old daughter, Hasti.
Hasti was born with a rare genetic condition called, Cornelia de Lange Syndrome, according to Brannigan.
"It affects Hasti's growth. She's not as tall as other kids. It impacts her cognition, so learning and speaking is difficult for her, and it causes seizures," Brannigan said.
MORE | Boy with rare cancer fights for his life amid experimental treatment
Brannigan told our sister station WPVI that it's going to get worse in a couple of years without treatment.
"She's a little child with dreams who wants to grow up to be happy and healthy and the sad truth is unless parents like me go out and do these crazy things, there is no money for rare disease treatments," Brannigan said.
Brannigan said he previously completed a grueling 700-mile walk in the United Kingdom. Since then, he's raised $1.2 million toward a $3.5 million goal, which he said is needed before clinical trials, research and gene therapy can begin.
"It's really humbling to know that total strangers in a foreign country want to help my little girl," Brannigan said.
Right now, they still have to raise another $2.3 million to reach their goal.
Brannigan's charity, Hope for Hasti, keeps track of his journey on Facebook and also accepts donations on their website.
MORE | 20-year-old battling cancer marries high school sweetheart