The American Chestnut was decimated by an invasive fungus, the chestnut blight, in the Appalachian region.

The American Chestnut tree was once a dominant species in the Appalachian forests but was nearly wiped out by an invasive fungus called Cryphonectaria parasitica, which causes chestnut blight. This fungus was introduced from East Asia in the early 20th century and spread rapidly across the Eastern U.S. The blight killed mature trees, and though the species still sprouts from roots, the mature trees do not survive, leading to the near-extinction of the American Chestnut in the region. Efforts to restore this species through breeding resistant trees are ongoing.