Finding information about world's fairs, or international expos, can be challenging as their name/titles change. You can search the CSUEB Library Catalog or WorldCat using words such as "worlds fair" or "expo* and art". A good overview can be found in both Encyclopaedia Britannica and Wikipedia.
The Smithsonian has a great page on the history of the world fairs. The Archives of American Art Blog published a story on the home movies of Hildreth Meier that she took of the murals at the New York World's Fair of 1939-40.
There are multiple resources on the web for the world fairs/expos. Some general sites are:
Pan-Pacific International Exposition (PPIE):
Golden Gate International Exposition (GGIE):
DIVA (a project of Academic Technology at San Francisco State) provides silent video of the art at the fair.