The National Register of Big Trees is a list of the largest recorded living specimens of each tree variety found in the continental United States. A tree on this list is called a National Champion Tree.
This list has been maintained since 1940 by American Forests, a nonprofit conservation organization. To be eligible, a species must be recognized as native or naturalized in the continental United States, including Alaska but not Hawaii, as documented in Elbert L. Little Jr.'s Checklist of United States Trees (Native and Naturalized), published in 1979 as Agricultural Handbook 541 by the United States Department of Agriculture. At present 747 native and 79 naturalized trees are eligible, for a total of 826 eligible species and varieties.
American Forests uses the following formula to calculate a point score for each tree so that they may be compared to others:
The current list of National Champion Trees is available online. In addition to the national list, several states, counties, and cities maintain their own list of local Champion Trees. Many are on public ground and can be visited without obtaining prior permission. The public may nominate trees as well.