This is a United StatesNational Register of Historic Places color coding colors legend, providing index to colors used in Wikipedia lists and articles on sites listed in the U.S.National Register of Historic Places.
Color options address nine categories of National Park System units automatically included on the National Register. These are (using the National Park Service abbreviations): IHS, NB, NBP, NBS, NHS, NHP, NMEM, NMP, NM.[1]
These are presented in order of rough counts of the number of each site (counts for several by quick inspection ofList of areas in the United States National Park System):