National Historic Landmark
From ENHLDWiki
There are only about 2,500 specifically listed National Historic Landmarks (NHLs) in the United States, in contrast with about 80,000 National Register properties. Concentrations of properties are listed as National Historic Landmark Districts such as the Butte-Anaconda-Walkerville NHLD. Within a NHLD all contributing properties are considered to be automatically listed on the National Register, but some properties will be or may be specifically listed individually.
In Butte, there are 14 separately listed National Register properties, and just one separately listed National Historic Landmark, the Burton K. Wheeler House. There are only 23 National Historic Landmarks in Montana. Anaconda has about 31 National Register-listed properties, including three sub-districts.
See National Register for more information and lists, and National Historic Landmark on Wikipedia. Also see the Montana list on Wikipedia.

