The United States Postal Service's official names for the cities in which ZIP codes are contained. This vector contains unique values, sorted alphabetically; because of this, they do not line up the other vectors in the way zip_codes and zip_centers do.
city_namesA character vector of length 19108.
Daniel Coven's web site and the CivicSpace US ZIP Code Database written by Schuyler Erle schuyler@geocoder.us, 5 August 2004.