 Initially the National Register consisted of those National Historic Landmarks designated before the Register's creation as well as any other historic sites within the National Park system.The passage of the act, which was amended in 1980, represented the first time the United States had a broad based historic preservation policy.While the National Register did not provide specific protection to listed properties it did require federal agencies to assess the impact of activities on buildings and properties listed or eligible for listing on the NRHP.