Getty Thesaurus of Geographical Names OnlineCompiles information drawn from published gazetteers, atlases, and encyclopedias, like Cambridge World Gazetteer, Columbia Lippincott Gazetteer, Encyclopaedia Britannica, Webster's Geographical Dictionary, Britannica Book of the Year,Times Atlas of World History, GEOnet Names Server (United States National Imagery and Mapping Agency), and United Nations Terminology Bulletin. Good source of information on name and spelling variants for places around the world. Historical information is far from complete (consult local gazetteers for more in depth information), but it makes a good starting point.