In the throes of the Great Depression, the members of the Civilian Conservation Corps planted more than 2.5 billion trees in public lands across the nation.

The effort, which took nine years, was a make-work project, designed to create jobs for people in a dead-in-the-water economy.

Their effort will be celebrated around the country today with National Public Lands Day, when thousands of volunteers will pick up shovels and pitch in to preserve parks in their neighborhoods.

In Portland, they will focus on the Riverton Trolley Park, which has lost some of its trails to erosion over the years.

“Just as FDR’s ‘tree army’ inspired a generation, (today’s) volunteer event gives today’s youth opportunity to follow in their footsteps and give back to our nation’s parks,” said Michael Bobinsky, Portland director of Public Services.

Portlanders of all ages are welcome to lend a hand and honor the workers of the past with a little labor of their own.

Here, in the aftermath of another financial crisis, although one not as deep as the Great Depression, we are also surrounded by public works projects paid for by the federal government with a goal of stimulating the economy.

Alternative energy projects, high-speed Internet and the reintroduction of passenger rail lines are the projects in Maine that may one day be held with the same regard as we view the park roads and cabins built by the CCC in the 1930s.

In order to spend the money more efficiently, it was mostly distributed through grants used to hire contractors to complete the projects.

That may have been the best way to cut down on wasteful government oversight, but it means that we won’t have the powerful symbol of a civilian force working for the common good with the focus of an army.

Nearly 80 years after they set out to work, people remember the C.C.C. and look with pride at what they accomplished.

Volunteers in Riverton Trolley Park, and thousands of other sites around the nation, can remind us of the “tree army” that went to work and changed the face of the landscape during a difficult period of history.