Archeological Investigations
The African Burial Ground (the latest National Monument in New York) was discovered during construction activities in downtown New York City. Road-construction projects are required to have subcontractors who investigate sites for archeological importance (Indian remains, for example). Archeological sites are sometimes preserved in secrecy, although some are pilfered by amateur archeologists. It is National Park Service policy to conceal the location of sensitive archeological sites by withholding location information on NRHP documents (or withholding NRHP documents altogether from the public).
Read more about this topic: Historic Preservation In New York