The men and women who serve the U.S. carry a heavy burden, even after they come home from a deployment, but two retired Marines are doing their own tribute to those who served.

There are about 4 million miles of public roadways in the United States, the longest of which is Route 20, a path that spans from Boston, Massachusetts to Newport, Oregon.

“Highway 20 represents the 20 years of warfare that our generation have gone to Iraq and Afghanistan," said Justin “JD” LeHew, who is walking across the country.

LeHew and Coleman Kinzer, also known as "Rocky," are retired Marines making the nearly 3,400-mile journey on foot.

“You can see a lot of things and have your own impressions about what America is, and then when you get out here and talk to them, it's like man, I really like this place,” Kinzer said.

The duo said the aches and pains are minor compared the hefty price tens of thousands of their fellow service men and women paid serving the country.

“When you tell people that there are 81,600 missing Americans since the end of World War II, their jaws hit the deck,” LeHew said.

Bringing them home is their mission on the longest road.

“It’s a long road home for a lot of these service members who have not returned home yet,” Kinzer said.

The men are collecting donations along the way to help support America’s Missing and Killed in Action, Gold Star Families and other charitable causes.

JD and Rocky are just getting started, but are already garnering massive support with passersby and business owners stopping them.

“They are guys that hear us coming through. They don’t have to give a damn what we’re doing, but they take time out of their day,” Kinzer said.

The men are eying a mid-November finish, knocking out about 20 miles a day.

“We joke with each painful step, say kind of like the boys in World War II, home by Christmas,” LeHew said.