When Franklin D. Roosevelt was sworn in as president in 1933, he took the helm of a United States brought to its knees by the Great Depression. With unemployment as high as 25 percent, millions were out of work and an entire generation of young people had lost hope in their futures, many living in makeshift shanty towns and riding the rails as hobos and drifters.

In his inaugural address, FDR latched on to an idea that was already being tested in states like California and Pennsylvania—to employ young people as an environmental army of tree planters, forest firefighters and soil conservationists.

“Our greatest primary task is to put people to work,” said FDR. “This is no unsolvable problem if we face it wisely and courageously. It can be accomplished in part by direct recruiting by the government itself, treating the task as we would treat the emergency of a war, but at the same time, through this employment, accomplishing greatly needed projects to stimulate and reorganize the use of our natural resources.”

On March 31, 1933, FDR signed the Federal Unemployment Relief Act, which recruited healthy unmarried young men to join what would become known as the Civilian Conservation Corps or CCC. The men, mostly uneducated and untrained, were paid $30 a month, $25 of which was sent directly to their families. They lived in racially segregated camps that operated under military-style rules, but they had money in their pockets and food in their bellies.

At its peak in 1935, the CCC enrolled 500,000 men at 2,600 camps across the country. The popular New Deal program was phased out by 1942 as the same young enrollees enlisted for World War II.

Over its nine-year run, the CCC accomplished its dual goals of rescuing a lost generation and restoring the nation’s squandered natural wealth. The following are just some of the CCC’s accomplishments.

When FDR was just 19 years old, he was put in charge of the Roosevelt family’s aging estate in Hyde Park, New York. Faced with a serious erosion problem, young FDR decided to plant thousands of trees. Later, as governor of New York, FDR spearheaded statewide reforestation efforts and purchases of neglected farms to turn back into productive timberland.

So it shouldn’t be surprising that reforestation was a major undertaking of Roosevelt’s CCC. The United States used to be rich with virgin forests, but unbridled logging had reduced the nation’s 800 million acres of timberland to just 100 million acres by 1933. Planting trees would not only restore a vital economic resource, but it could combat the rampant soil erosion that contributed to environmental disasters like the Dust Bowl.

Planting trees was so closely associated with the CCC that it was nicknamed “Roosevelt’s Tree Army.” By one estimate, the hardworking enrollees of the CCC planted 3.5 billion trees from 1933 to 1942, which is more than half of the total amount of trees planted in America as part of reforestation efforts.

Not only did the CCC plant billions of new saplings, but it also restored and rehabilitated overcrowded forest stands by thinning dead trees. Other CCC enrollees were charged with tending experimental forest plots that led to innovations in healthy forest management.

The Department of Interior put CCC recruits to work expanding the country’s nascent national and state park systems. While a number of major national parks existed in 1933—Yellowstone and Yosemite date back to the 19th century—there were still several states without a single state park, including Virginia, West Virginia, South Carolina, Mississippi and New Mexico.

Over the nine-year run of the CCC, a total of 2 million CCC workers labored to create new national and state parks and make existing ones more accessible by paving roads, cutting trails, and building cabins and campsites. In total, there were 194 CCC work camps in 94 national parks and 697 camps in 881 state and local parks across the US.

Two well-known national parks were built almost entirely by CCC labor: The Great Smoky Mountains National Park straddling the border of North Carolina and Tennessee, and the 600-acre Big Bend National Park in Texas. In addition, the CCC helped to create a total of 711 new state parks across the country.

During the nine years that the CCC was operational, the annual acreage of U.S. forest lost to fire sunk to its lowest point ever, despite the fact that a record number of forest fires were reported. That’s because tens of thousands of young CCC enrollees were employed as either full-time or emergency firefighters.

Teams of permanent CCC firefighters patrolled vast stretches of forest on foot, by truck, by airplane and even canoe. When a blaze broke out, nearby CCC camps were enlisted to attack the fire with everything they had—handheld axes and hoes, shovels and saws, and the occasional bulldozer.

In one memorable campaign, the stalwart CCC firefighters took on the mysterious subterranean coal fires near Gillette, Wyoming. The fires, which could send flames 20 feet in the air from exposed coal seams, had been burning for as long as residents could remember. The CCC workers smothered some of the fires with sand and dug burning material out of others, successfully bringing 17 separate blazes under control by 1937.

The total number of hours logged by CCC firefighters from 1933 to 1942 was the equivalent of 6.5 million days. Tragically, 47 CCC firefighters also lost their lives in the effort.

Fire prevention was just as important as fire fighting. Droves of CCC men were assigned to improve emergency access to forest lands by cutting tens of thousands of miles of truck roads, breaking new trails, and stringing countless miles of telephone lines to facilitate communication between fire-fighting units.

Lookout towers were critical to spotting small fires before they grew into forest-gutting blazes. CCC workers constructed more than 3,000 of these towers, including the stone masonry Mount Diablo Lookout Tower outside of San Francisco commanding impressive views of the Cascades and Sierra Nevada mountain ranges.

CCC crews also thinned dead logs and timber from fire-prone areas and cut preventative fire breaks to slow the progress of a potentially disastrous blaze. One of the largest of these fire breaks was the Ponderosa Way in Northern California, a 600-mile scar separating the dry brushland from the timber-rich forests above.

The CCC also oversaw the construction of large water storage basins and collection ponds to have a ready water supply to battle future wildfires.

The Soil Conservation Service was second only to the Forest Service for the largest number of CCC camps under its direction. After decades of improper land use—clearing trees to create more farmland, failing to plant cover crops in fallow fields—and years of drought conditions, erosion was threatening much of America’s farmland. By 1938, there were more than 500 active CCC soil conservation projects in 44 states employing 60,000 young men a year.

The CCC workers planted trees to serve as windbreaks and soil anchors. They healed gullies and redirected water back toward crops. And they trained farmers in modern soil conservation techniques that would lead to healthier land and bigger yields.

One of the most innovative and effective tools of the CCC was the terracing of hilly land to create level fields with less water runoff. Terracing was no small undertaking, requiring engineers, surveyors and heavy machinery. Over the life of the CCC, more than 30,000 miles of terraces were built and thousands of young CCC workers gained technical skills that served them well in future careers.

Downhill skiing was not a thing in America in the 1920s. There simply weren’t any dedicated ski trails, let alone conveniences like rope tows or ski lifts. But thanks to the CCC and a forward-thinking forestry official in Vermont, America got its first ski runs in the 1930s.

Perry Merrill, the state forester of Vermont, had attended forestry school in Sweden, where he witnessed the Scandinavian passion for downhill skiing. Merrill dreamed of bringing the sport to the craggy hills of his home state but lacked the resources to cut and clear miles of trails. Until, that is, he was put in charge of a CCC team of 25 hardy men in 1933.

Over the next few years, the tireless CCC workers cut legendary New England trails with names like Stowe, Wildcat, Cannon and Thunderbolt. Out West, CCC workers also cut the first ski runs in Sun Valley, Idaho. The first rope tows were installed in the late 30s and Americans fell in love with skiing, thanks in no small part to the CCC.