Try Interlibrary Loan!
Create a free account, and then log in to request a copy of an article or book. Articles are emailed to you and requets can usually be filled within a couple of days. Books take 3-5 days on average and are sent to Ablah Library for you to pick up.
These databases are very useful for finding secondary research (criticism and theory) about literature. Search for the title of the book, the author, and/or a keyword such as "Puritans" or "slave narratives".
These databases will be useful when searching for secondary research related to the time period or historical movement. JSTOR in particular includes journal issues back to the very first issue (limit your search to the decade(s) after an event happened to see what was written about it at that particular time).
The following is a small selection of interesting titles. Use the Library Catalog to search the full collection.
Try the Subject Heading American literature--History and criticism