The USC community has another wonderful resource for historical study, Cambridge Histories Online. It includes the completely searchable full text of the 247 volumes in the Cambridge Histories series. You can explore volumes about American and British history; economic history; the histories of science, music, literature, religion, and other fields of study; social histories; and specialized topics like the history of warfare and British urban history. If you're on the USC campus or using a remote connection, you can access the online resource here.
The Cambridge Histories provide a wealth of historical information about nearly every imaginable topic.