The Cambridge Histories Collection includes multi-volume works on many geographical units and historical themes, and can help you with the general narrative of a time period and major academic debates on the issues.
Deciding on a topic can be one of the hardest parts of the research experience. As you explore areas of interest to you, it's important to discover what other scholars have already written on the subject, and find new areas of inquiry to pursue.
Subject encyclopedias, bibliographies, and test searching in subject databases can help you get up to speed on what scholars have been working on, get ideas on new directions to follow, and get a list of readings you may want to consult and engage with.
Video tutorial courtesy of the librarians at North Carolina State University.
The entries in subject encyclopedias are written by scholars in the field, and often include recommended readings or bibliographies. These can be great starting places if you're new to a topic, or are feeling overwhelmed and need some recommendations on where to start your reading.
Encyclopedia of Women in American History by 
Handbook of American Women's History by 
