The National Register of Champion Trees is a list of the largest tree specimens found in the United States as reported to American Forests by the public. A tree on this list is called a National Champion Tree. The National Register of Champion Trees has been maintained since 1940 by American Forests. To be eligible, a species must be recognized as native or naturalized in the United States. American Forests uses the following formula to calculate a point score for each tree so that they may be compared to others: