The Virginia Round-leaf Birch only grows naturally in Smyth County, Virginia at an elevation of 2750' feet. It is so rare that it was thought to be extinct until 1975! Currently, there are less than ten individuals left in the only natural population, but since there are artificially propogated populations, the species is considered threatened and no longer endangered.
The one I spotted is part of a Memorial Grove at the Virginia Tech Duck Pond. The grove is dedicated to Peter P. Feret, a faculty member who helped bring the species back from the brink of extinction.