Carolyn Cannamore, representing Wells House in Gaithersburg, uses her cane to welcome walkers at the end of the walk on the National Mall. Fannie Mae has sponsored the Help The Homeless walk for many years but this is the last one. (Dayna Smith/FOR THE WASHINGTON POST)

It has been a pre-Thanksgiving ritual for many in the Washington area, an opportunity to reflect on personal good fortune, get some fresh air and spend a few hours walking for a humanitarian cause.

But on Saturday, the thousands of marchers in the 24th annual Fannie Mae Help the Homeless Walkathon gathered on the Mall for one last time.

The troubled, federally chartered mortgage giant is ending its three-mile walk in Washington, saying that decentralizing it will more efficiently raise money. Fannie Mae plans to promote neighborhood marches in cities including Atlanta, Dallas, Chicago and Philadelphia.

“We hope to raise even more funding,” said Fannie Mae President Michael J. Williams, one of several people to address the crowd before the march began shortly after 9 a.m. on a chilly morning.

In the Washington area, which has more than 12,000 homeless people, about 700 mini-walks were held last year, raising $6.5 million, according to Fannie Mae. The Mall march itself contributed about $1 million.

On Saturday, each of the participants — from schools, religious institutions, businesses, nonprofit groups, scouting troops and community organizations — paid $20 to $35 to walk.

The need for more assistance for the homeless is acute. More than 40 percent of those without homes in the Washington region are families; 25 percent are children.

For the Henriksen family of Burtonsville, the traditional trip to the Mall to march began several years ago when the three children were much younger. On Saturday, Megan Henriksen, now a fourth-year engineering student at the Rochester Institute of Technology, was the only one of the siblings available to make the trek with parents Jim and Maureen. They didn’t realize that this would be their last time.

“That’s too bad. I did not know,” said Jim, an accounting consultant for the federal government.

“You go out. It’s cold. It makes you think about homelessness even more,” said Maureen, who works on child-support enforcement at the Department of Health and Human Services.

Del. Eleanor Holmes Norton (D-D.C.) and D.C. Mayor Vincent C. Gray (D) exhorted the crowd, which organizers estimated at more than 10,000, to continue their efforts. “Government is doing less, so we must do more,” Norton said.

Gray said the District should lead the way to end homelessness. “Let’s be the first city in America to end homelessness among our children, [our] youth and our families,” he said.

As marchers made their way to the staging area — where there were T-shirts, a disc jockey, Redskins cheerleaders, and snacks and water — many passed visible evidence of Washington’s nagging homeless problem: people who were wrapped in blankets and huddling in office doorways and on heating grates.

Those scenes worry DelanteHenderson, a senior at the Washington Mathematics Science Technology charter high school, who was at the march with several classmates.

“I want to be part of something big to help out the community,” said Henderson, who also volunteers at a child-care center and is hoping to attend college in New York or South Carolina.

For Lindsey Buss, president of Martha’s Table, a nonprofit that helps the homeless in Washington, the end of the march is bittersweet.

“You may find the issue recede from consciousness to some degree,” Buss said, pointing to the high visibility that a march on the Mall can provide to a cause.

But Martha’s Table is already trying to adapt, working with Fannie Mae this fall to organize 21 mini-walks in the Washington area, six more than last year. The funds go directly to help Martha’s Table, Buss said.

“It is hopeful,” he said.