By the 1970s, Prospect Park was beset by crime; a 1974 report found that 44 percent of city residents would warn people to stay away from the park under any circumstances. The mayoral administration of Ed Koch formed plans in 1980 to turn over the administration of the troubled Prospect Park Zoo to the Wildlife Conservation Society. Over the next seven years, the city invested $17 million in cleaning up the park, including $10 million in federal funds from a Community Development Block Grant. Annual visitor numbers had nearly tripled to 5 million between 1980 and 1987. During this period, Prospect Park also received two historic designations: it was made a New York City Historic Landmark on November 25, 1975, and was listed on the National Register of Historic Places on September 17, 1980.