GADM has been developed by Robert Hijmans, in collaboration with colleagues at the University of California, Berkeley Museum of Vertebrate Zoology (Julian Kapoor and John Wieczorek), the International Rice Research Institute (Nel Garcia, Aileen Maunahan, Arnel Rala) and the University of California, Davis (Alex Mandel), and with contributions of many others.
We thank many individuals and organizations for sharing data, in particular the International Center for Tropical Agriculture (CIAT, Andy Jarvis), ICRISAT and ILRI. Andy Nelson provided much of the country level codes and membership information. The development of GADM was partly supported by the Gordon and Betty Moore foundation and USAID.
Our goal is to map the administrative areas of all countries, at all levels. We use a high spatial resolution, and of a extensive set of attributes for each spatial feature. This is a never ending project, but we are happy to share what we have so far. Please contribute in whatever way you can by sending us a message to point out errors, or even better, to send an improved file for a country of your interest.
Here are links to other sources of administrative area data and related information.