By Andrea Lucia

DALLAS (CBSDFW.COM) – Hundreds of people took up the challenge: to walk twenty hours straight, often carrying a heavy load.

From Reverchon Park in Dallas, they began with backpacks, fire hoses, or even thick logs tossed over their shoulders – circling up and down the Katy Trail.

“Mine weighs 55 pounds today,” said Steve Merritt, pointing at his large camouflage backpack.

Now in its second year, the event, Carry the Load, helps raise money during the Memorial Day weekend for non-profits benefiting military service members, police, and firefighters.

“These people do what they do every day to keep us safe, least I can do is walk 20 hours,” said Kenneth Fowler, who is walking in honor of his grandfather, a veteran of the Air Force.

“We wanted to give the public an opportunity to come out and celebrate Memorial Day in a meaningful way,” said co-founder Stephen Holley.

The load they carry, though, often seem to represent the emotions they carry, as well.

Margy Agar is carrying pictures of her daughter, Sgt. Kim Agar, who died after suffering a head injury while serving in Iraq.

“I’m proud because she’s my hero – and I want others to know about her,” said Agar. “I’m carrying her load. I’m carrying her forward.”

Stretching through the night, the walk will end just after noon on Sunday. More than six hundred people began it; about a hundred are expected to finish.  So far, the event has raised 470,000 dollars.