National Register of Historic Places
The National Register of Historic Places is the official listing by the federal government of places, buildings, sites, and communities that have historical significance.
In order to become eligible for listing the site must meet one of four specified criteria (and, often, it will meet more than one): Event (a contribution to American history), Person (associated with a significant historical person), Design/Construction (a building being distinctive by its architecture and/or construction, an example would be a building designed by Frank Lloyd Wright), and/or "Information potential" (the site has yielded, or has the potential to yield, information pertaining to prehistory or history).
In addition certain sites are "excluded" from consideration: religious properties, buildings which have been moved, birthplaces or gravesites of important persons, cemeteries, reconstructed properties (an example was Soldier Field, the home of the Chicago Bears; a significant redevelopment of the facility caused it to lose its designation), commemorative properties (such as statues), and properties which have not yet become 50 years old. However, the "exclusions" are not consistently followed: for example the Register contains thousands of churches and other religious buildings.