administrator of areacodes) NANPA.com: Areacodes maps (页面存档备份,存于互联网档案馆) (per state maps of area code assignments; some maps are outdated) Canadian Area Code Maps
Population and Housing Unit Estimates. [June 9, 2017]. (原始内容存档于2017-05-29). 2018 FIPS Codes: 2018 State, County, Minor Civil Division, and Incorporated
Observatory, Alfred University, NY 785: Fitz-Randolph Observatory, Princeton, NJ 786: U.S. Naval Obs., Washington (since 1893) 787: U.S. Naval Obs., Washington