The National Register of Historic Places (NRHP) is the United States government's official list of districts, sites, buildings, structures, and objects (all called "properties") worthy of preservation. The list is kept by the National Park Service. The National Historic Preservation Act of 1966 (NHPA) created the National Register and the method for adding properties to it. There are more than one million properties on the National Register, 80,000 are listed by themselves. The rest of the properties are smaller "contributing properties" that are part of historic districts. Each year around 30,000 properties are added to the National Register as part of districts or through individual listings. A few are National Historic Landmarks.