STATE COLLEGE -- About a mile as the crow flies from Beaver Stadium, where the Penn State faithful gather each fall in search of gridiron glory, stands a chestnut tree.

On this late summer afternoon the chestnut's branches are heavy with burrs -- those unique spiny balls that typically protect three nuts. There was a time when any child of the Pennsylvania woods was as familiar with the chestnut burr as an apple, and for many of the same reasons -- good eating, and good for pelting your friends when they're not looking.

In a good year (and this year appears to be good) a single tree can bear more than a thousand burrs -- a prolific bounty that bends this particular chestnut's branches away from the sky and down toward the ground.

Beyond the high deer fence and away over the hill, the remnants of the previous Penn State football game still litter the grounds of Beaver Stadium. There on the hill the stadium stands alone, a shrine of sorts to human athleticism that dwarfs the parking lots and fields that surround it. Back on its sheltered hillside, the chestnut tree also dwarfs the other trees around it.

For another group of faithful (perhaps not as numerous as those who gather at the stadium) this tree also stands as a shrine, a symbol. Rather than celebrating the prowess of the athlete, however, this tree stands as a reminder of humanity's complicated legacy -- of our hubris, and the danger of good intentions, of our ignorance and, perhaps to some degree our vanity; but also as a symbol of hope, of a long promise -- as yet unfulfilled -- and of the enduring, relentless drive that often marks the best of the human spirit.

It is this tree, growing tall and straight on the hillside near State College -- and its relatives and descendants in orchards scattered across the Eastern Seaboard -- that might finally fulfill the hundred-year-old quest to save the American Chestnut, to bring back a tree that was once counted among the kings of the forest but today exists only in scattered enclaves and the memories of our oldest generations.

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Chestnut trees grow in an orchard outside Penn State in Centre County.

At the turn of the last century -- before the rapid mechanization of the 20th century and the rise of the suburbs, before highways crisscrossed the land, before there was a Department of Environmental Protection -- there was the American Chestnut.

Tall and straight, the quick-growing tree was common in the mountainous woods of Appalachia and along the edges of the farm fields that covered Pennsylvania and much of the Eastern Seaboard. By some estimates, the American Chestnut accounted for one in five trees that grew along the mountain chain; billions of gray trunks reaching up to create a broad canopy of slender green leaves, each with their distinctive wave-curled edges.

The chestnut's range stretched south from Maine and along the New England coast into New York and New Jersey. It swallowed Pennsylvania and reached west into Ohio. Further south, it crowned the mountains through West Virginia, Kentucky, and Tennessee. It was common in northern Mississippi, Alabama, and Georgia, and could be found in the western reaches of North Carolina and Virginia.

The chestnut was beloved for its nut, which would fall by the bushelful at the first frost of the year. The trees provided such a bounty that in some areas it became a staple of peoples' diets through the fall and early winter, stored by the sackful near the fire, waiting to be roasted. Some areas collected the nuts commercially, which were then shipped by rail to be sold in the cities. The nuts also provided an important feed for livestock, especially pigs, and the abundant wildlife of the region which in turn were important sources of meat for peoples' diets.

READ MORE: "An oral history of the American Chestnut" or "Historical significance of American Chestnut to Appalachian culture and ecology"

Wood from felled trees was also a source of lumber and timbers, which were in wide use as building materials for homes, railroad ties and the telephone poles that were quickly binding the nation together. In 1909, the value of the chestnut to the timber industry was estimated to be around $20 million, or a half-billion dollars today after accounting for inflation. Almost every part of the tree was used in some fashion; even the bark was an important source of acid for the tanning industry, all of which provided not just substance but also sources of income for rural communities.

The American Chestnut has been called "the perfect tree" for its myriad of uses (food, furniture, lodging, industry, etc.) -- one that carried the people who lived along its range from cradle to grave. It provided a means of the self-sufficiency that became a part and parcel of Appalachian culture that continues today.

The tree was so ubiquitous that its importance could only be underscored by how quickly it would disappear.

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A map showing the native range of the American Chestnut circa 1900.

The death of the American Chestnut was not the first ecological disaster in North American caused by man nor would it be the last. But it was one of the most well- documented, and one that occurred amid the environmental awakening of the late 19th and early 20th centuries. The speed at which it unfolded made it even more dramatic.

It began with a few small embers -- the tiny spores of a fungus (Cryphonectria parasitica) that likely emigrated to North America via shipments of Chinese or Japanese chestnuts, which were imported for agricultural purposes.

The fungus, which is airborne, infects a tree through cracks in its bark -- even minute cracks caused by branching or by a squirrel's claws. It then begins growing under the bark and ultimately spreads to encircle the trunk of the tree, secreting an acid that is toxic to plant cells.

Eventually after girding the trunk the fungus will cut off nutrient supplies to the upper trunk and branches, killing everything above the ring caused by the infection.

Within two or three years of initial infection the tree is dead -- only the stump and root system remain alive as silent witnesses to a once-great tree. The stump and root systems will, over time, rally in a quest for survival and sprout a new series of growths (root shoots) in an attempt to regrow the tree. But while new growth might develop, it will not last -- after a few years the fungus will once again re-infect the tree, again encircling it in an embrace of death. The stump and roots will once more go dormant until they rally yet again and the cycle repeats.

Asian chestnuts have evolved alongside the fungus and have developed defenses against it. When infected, the trees will encircle and contain a fungal infection with a bulbous hoary growth that looks not unlike a set of pouting lips. The American Chestnut had no natural defenses when the fungus reached these shores -- and it paid a terrible price.

When it was first discovered in 1904 in New York City, the mysterious pathogen was simply that, a mystery -- it would be two years before it had been identified as a fungus and given its common name, the Chestnut Blight.

Initially it was hoped that at worst, like a house fire that was prevented from spreading, the blight would burn itself out and go away of its own accord.

But this was a fire with a continent's worth of fuel awaiting a spark.

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A chestnut orchard in Philadelphia circa 1900.

The first rule of fighting any fire is containment -- prevent the fire from spreading, from reaching new fuel, from exerting its relentless will to consume and grow. So when a virulent disease beings to spread, we enact quarantines to try and prevent an outbreak from becoming an epidemic.

After being first identified in New York City in 1904, the fungus spread like a wildfire through the city's parks. By 1912 every American Chestnut tree in the city was dead, and outbreaks had been reported in other states.

In Pennsylvania the blight was first reported in 1908 in Montgomery County. Further investigation over the following two years by the state's nascent Forestry Commission confirmed the disease's presence but also determined that it was largely confined to the eastern portions of the state.

As it became clear that the blight was sweeping through the Northeast, Pennsylvania rallied to defend the tree. In a letter to the state legislature in 1911, then Gov. John Tener said it was clear that chestnuts in New Jersey were "doomed to destruction." Encouraged by an early experiment conducted by the U.S. Department of Agriculture, Pennsylvania established a Chestnut Tree Blight Commission and set about establishing a firebreak, or bulwark, against the spread of the disease.

In the eastern half of the state the disease was deemed to be beyond control. The commission's goal therefore was to contain the disease east of the Susquehanna by cutting down and removing any infected trees discovered west of the river. Unfortunately, by the time the commission became organized and active, the blight had jumped over the river and was rapidly spreading west.

Pennsylvania's plan was controversial. A year after the work had begun, Tener called for a conference on the blight. Scientists and state delegates from across the eastern United States traveled to Harrisburg to discuss the disease and Pennsylvania's efforts to stop it.

The scientific community itself was split. Several scientists argued (correctly) that the program was doomed to failure and based upon incomplete investigations. New York professor F. C. Stewart, who addressed the conference, argued "it is better to attempt nothing than to waste a large amount of public money on a method of control which there is every reason to believe cannot succeed." Rather than waging a war with the disease, Stewart and others argued that efforts should be directed toward further scientific study of the blight.

However, the debate occurred against the backdrop of the rapid industrialization of America, at a time in which almost anything seemed possible: Less than a decade earlier the Wright brothers had flown at Kitty Hawk; the Ford Model T was providing transportation to the masses; and Harrisburg itself had been transformed by electric power only a few decades before.

From the address of R. A. Pearson, of New York, to the Pennsylvania Chestnut Blight Commission in 1912

To do nothing, argued R. A. Pearson of New York, who chaired the conference, would be "un-American."

Pearson: "It has been suggested that we should wait patiently until the scientists have succeeded . . . but that is not the way that great questions are solved. If we had waited until the application of steam should be thoroughly understood, we would be still waiting for our great trains and steamboats, which are the marvel of the age."

Pennsylvania would march on.

If the plan was the product of hubris, Stewart and the other scientists were perhaps just as guilty, convinced that in the end scientific inquiry and a faith in knowledge would carry the day.

"There have been other epidemics, and other kinds of trees and plants have been threatened with destruction through disease, but such a thing has never actually happened," he said. "So far as known, no other plant has ever been exterminated by disease. It is unlikely that the chestnut will be exterminated."

READ MORE: The Pennsylvania Chestnut Blight Conference (1912)

Over the course of the two-year war a small army of commission workers scoured the woods of western Pennsylvania, searching for and cutting out infected trees. In its final report to the legislature, the commission reported more than 30,000 trees had been removed from the state's forests during the two summers its men were active.

A map showing the work of the Pennsylvania Chestnut Tree Blight Commission, which attempted to stop the spread of the chestnut blight in 1912-1913. Red dots indicate locations where the blight was detected.

"It is sufficient to say here that the progress of the disease in the western half of the state has been set back five years, and west of the line extending from Bradford to Somerset counties there is little infection," wrote Winthrop Sargent, chairman of the state's chestnut commission.

Still, despite the commission's best efforts, outbreaks of the disease had been found to leapfrog the fire line and establish pockets of the blight west of the quarantine zone. Without regular (and, at the time, expensive) efforts to contain the fungus, it was only a matter of time before the state's chestnut forests succumbed. When the commission requested in 1913 that the state legislature reauthorize its $275,000 bi-annual budget, it proved too much for the state to afford.

When the legislature balked at the commission shutdown, Sargent issued a dire (if accurate) assessment of the chestnut's future in Pennsylvania with the end of the program: "The complete loss of the present commercial stand of chestnut in Pennsylvania, which, now that the Commission has ceased work seems absolutely certain, is a calamity with will be fully realized only in the future," he reported. "... The Commission closes its work with regret, knowing well that the blight will now spread over the State without hinderance."

READ MORE: The Pennsylvania blight commission report (1913)

Despite their best efforts, it is unlikely the quarantine line would have made a difference in the long run. The fungus is not like a fire -- it won't burn itself out. Instead, it circulates among other tree species, haunting the forests.

In the end, the Chestnut Blight spread across the East Coast at an alarming rate -- some estimates as high as 50 miles per year -- devastating forests in its wake. In the rural communities that lived alongside the chestnut, it appeared, according to one contemporary, as if "the whole world was going to die."

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Members of the Pennsylvania Chestnut Blight Commission with trees felled in an attempt to stop the blights progression in the state.

An entire species of chestnut -- as many as four billion trees -- died as the blight ripped through the Appalachian forests. The species, once so prolific, once such an intertwined part of life in rural Appalachia, was deemed to be functionally extinct by the 1950s.

Even as the trees were dying, researchers were trying to find ways to stem the tide beyond the Sisyphean task of containing the epidemic. One of the most promising was with the very trees that caused the blight to be brought to the United States in the beginning -- the asian chestnuts that had evolved alongside the fungus.

In the 1920s, federal department of agriculture researchers began interbreeding both Japanese and Chinese chestnut trees with American stock, but they met with mixed results: Hybridized trees were often either not blight resistant enough, did not have the characteristics of the American species, or were stunted or lacked the hardiness necessary to survive outside of a nursery setting.

A second breeding program, begun by the Brooklyn Botanic Garden and later transferred to Connecticut, met with similar results. Eventually, after almost a half-century of effort, both breeding programs were shut down, leaving only remnant stands of crossbred chestnuts in former nurseries (including several in Pennsylvania state forests, where visitors can still come across these old orchards).

READ MORE: "The future of the Chestnut Tree" Arthur Graves (1914)

For years, it seemed the American Chestnut was doomed to survive in its diminished state, existing only in the memories of those who grew up under its boughs.

The programs' true legacy, however, survived in two trees -- named the "Clapper" and "Graves" trees after their breeders, both of which showed promising disease resistance and characteristics of the American species.

Decades later, those two trees would become the cornerstone of modern efforts to save the species.

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A juvenile American chestnut tree growing at the chestnut research orchard in the Arboretum at Penn State University, September 11, 2017.

Even if the fungus kills a tree, it can't kill the roots. Those survive, gathering nutrients until they can once again grow toward the sky. Like the blight-choked death of an American Chestnut, the end of the federal breeding program was not the end of man's attempt to save the species.

In farmers' fields, on university grounds, and on wooded lots across the tree's former range, scientists and growers continued to try and find a way to save the tree.

One of the men who became interested in saving the chestnut was Charles Burnham, a corn geneticist from Minnesota who, along with others in the 1980s began a new breeding program. To fund their efforts, they formed The American Chestnut Foundation, a private nonprofit organization.

Burnham theorized that if a blight resistant tree could be bred between the American and Chinese lines, then it should be possible to further interbreed that stock with additional American Chestnut lines (so called backcross breeding). Each generation would become successively more "American" in nature -- and a fraction would also carry the genes for blight resistance.

READ MORE: "The backcross breeding program of the American Chestnut Foundation"

It was a common practice in the field crops Burnham studied. However, unlike corn or other plants which mature and reproduce within a single season, an American Chestnut takes between five and seven years to reach maturity.

They would begin with the remnants of the earlier breeding programs, the Clapper and Graves trees, and breed them with other surviving American Chestnuts. It was expected that, counting the initial American-Chinese cross, it would take six generations -- or 30-plus years -- of breeding to create a tree that was 15/16ths American and retained resistance.

Each breeding generation would produce hundreds, if not thousands of trees, of which only a handful would have the traits necessary to further the line. It would be one of the most ambitious scientific conservation programs ever: A 30-plus year breeding program on a scale never attempted before and with no guarantees of success. And, with the end of the USDA program, would be undertaken almost entirely by volunteers and funded by donations.

The foundation rolled up its sleeves. It built a plantation in Virginia, and sprouted chapters across the East Coast, each of which also began working on the breeding program.

In Pennsylvania, the chapter's fields are located outside of Penn State.

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Controlled pollination is done by bagging flowers on selected trees to keep unwanted pollen away and introducing pollen from trees with a high level of blight resistance. American chestnut tree blight resistance breeding at the chestnut research orchard in the Arboretum at Penn State University, September 11, 2017.

The chestnut on the hill -- the tallest tree on Penn State's plantation -- has been surviving here for 18 years and is a fifth-generation member of the American Chestnut Foundation's breeding program. It is the oldest chestnut that has survived at Penn State, the scars on its trunk evidence of its battle against the blight.

From where the tree stands the hillside tumbles down toward a creek, the slope covered in clusters of chestnut trees, grouped by family and age. Each group begins as seedlings grown from one of the disease-resistant lines, crossed with a different American Chestnut parent tree. As the trees grow, they are inoculated with the fungus to test their resilience. Typically less than half of the trees will survive. Those that do are then used in further breeding trials.

Some family groups are doing well -- their trunks are tall and straight, the canopy created by their branches keeps the ground under them clear of growth and their limbs full of burrs.

Other groups are stunted, their trunks sheared off a foot or so above the ground, the remaining trunks covered with root shoots as the trees struggle to survive against the blight. And some are in between, gnarled and twisted compared to their more successful cousins.

But it is the success of the solitary giant and its progeny, and the related trees at the foundation's plantation in Virginia that have provided hope that after 90 years the American Chestnut may once again return to the forests.

In a scientific paper published this year, researchers concluded it was now only a matter of time before the foundation's lines could be re-introduced into the wild. After 30 years and tens of thousands of hand-pollinated chestnut trees, the quest to save the American Chestnut is tantalizingly close to success -- and yet remains incomplete.

Steve Hoy is the orchard manager at the chestnut research orchard at Penn State. American chestnut tree blight resistance breeding at the chestnut research orchard in the Arboretum at Penn State University, September 11, 2017.

While the current generation of American Chestnuts shows resistance to the fungus, they might not yet be resistant enough for the species to survive in the wild.

In the analysis of the program, lead author Kim Steiner, a professor of forest biology at Penn State College of Agricultural Sciences and director of the university's arboretum, the chestnut breeding program "may need an additional one or two generations of recurrent selection to maximize resistance."

Their current estimation for program completion: 2022. Even then there will still be work to be done. The various lines will have to be interbred again and again to ensure maximum protection from the blight.

Young trees will have to be carefully selected and cared for before being transplanted back into the woods. Natural selection will likely claim more than 75 percent of the wild seedlings before they grow to become mature trees.

The breeding program will likely be combined with another American Chestnut Foundation initiative in New York, which since the 1990s has been attempting to genetically modify the species to build in blight resistance using a common gene found in wheat. The program has successfully grown trees with the genes, and is seeking regulatory approval to grow them en mass for public planting.

Between the two programs, and for perhaps the first time in recent memory, the finish line is in sight. The vision of a naturally-growing American Chestnut -- standing on a hillside in the forests of Appalachia, is more than a memory or a dream. It is close -- so close -- to being a reality for the first time in more than a half-century.

"The rescue and restoration of American chestnut stands as one of the most difficult, prolonged and complex single-species conservation tasks ever attempted," Steiner and his co-authors write. "However, nine decades after chestnut breeding work began ... the reality of a solution is now less a matter of time and conjecture than has ever been the case before."