Works that analyze, assess or interpret an historical event, era, or phenomenon. Generally written well after the events that are being researched
Books
Be sure to use scholarly books that are from a University publisher or a well-known scholarly publisher.
One Search & EBSCO eBooks will be the best place to find scholarly books.
Journal articles
Be sure to use peer reviewed articles. You can check if the article is peer reviewed by looking at the journal's website
EBSCO's America History & Life, Gale Power Search and JSTOR are the best databases to use. Remember, databases allow you to refine your search to only peer reviewed articles.
Reviews
You can find book reviews in EBSCO databases. You can also find them in Gale Literature.
Encyclopedias
Encyclopedias are a great place to start with your research. Many of the Library's primary source collections contain analysis that is considered a secondary source. However, you should focus on citing scholarly books and peer reviewed articles in your paper.
This video discusses the difference between primary and secondary sources in historical research: