American Chestnut trees once made up about 25% of the hardwoods from Pennsylvania down to northern Mississippi and Alabama. Mature Chestnut trees were huge - they dwarfed giant oaks - and I've seen figures suggesting they made up as much as 20% of the biomass in their habitat.
Unfortunately, American Chestnut trees are not immune to the chestnut blight, while Japanese and Chinese chestnut trees are.
Around 1904, asiatic chestnut trees were introduced to the New York Botanical Garden, along with the chestnut blight. The blight began killing 50 miles of American chestnut trees a year. We lost around three billion American Chestnut trees to the blight.
There are a few locations where American Chestnut trees still grow, either because the trees had a natural resistance to the bight or were protected from the blight. Other American Chestnuts are being introduced, grafted onto Asiatic roots. New American Chestnut trees continue to sprout from the roots of dead trees, but they die from the blight by the time they hit a height of six feet.
How did I learn about these trees?
I went backpacking in the Mountain Bridge Wilderness Area in South Carolina. Within it, there's an American Chestnut tree graveyard. Although most AC trees were logged (they're huge and not susceptible to rot), this grove was protected on two sides by rock cliffs.
Ninety years after the trees died, the ground is littered with half-rotted giant trunks.
I was backpacking with an arborist, who told me about the trees. He just sat on one trunk with his head in his hands.
One of the interesting things of those areas is that in a large part it was all clear cut at some point. People often think these trees have been there forever. Not the case. It does show the resilience of nature and the ability to come back and the ability of humans to manage property.
There is an example of a 40ft chestnut tree growing near Bat Cave NC that although stunted has some natural resistance to the blight.