Geographic Midpoint Sources

US city data

The data for US cities was taken primarily from the US website. Look for the "Places" download (filename on the following page.
Census 2000 Gazeteer Files

World cities data

The data for world cities was taken primarily from The following sources.

The GEOnet Names Server has a data file for each country (excluding the US) and is available at:
GNS country files

Toponymic information is based on the Geographic Names Data Base, containing official standard names approved by the United States Board on Geographic Names and maintained by the National Geospatial-Intelligence Agency. More information is available at:
Products and services
. The National Geospatial-Intelligence Agency name, initials, and seal are protected by 10 United States Code Section 445.

The World Gazeteer website. The download filename is
World Gazetteer Download Page

Data for the 3000 largest cities in the world.
World's Largest Cities

Data notes

The data from the above sources may contain inaccuracies and errors. For most cities the English name has been used, although many cities have one or more alternate spellings. Some political entities and boundaries may vary among different sources. The data sources have rounded the latitude and longitude for some cities to the nearest 10 minutes, therefore, a city's coordinates may not always coincide exactly with the position of the city on a map.