After finding secondary sources in the catalog, you'll have a good sense of the keywords to use for your topic.
Now, try one of your searches from before, but limit the publication box to your time period.
EXAMPLE: primary sources about the slave trade during the Civil War
Use The main library catalog to find primary sources by limiting to publication date or using the subject headings below.
Writings by confederate soldiers during the Civil War
Use Subject Terms to find historic materials in the collection. NOTE: DO NOT LIMIT PUBLICATION DATE RANGE FOR THESE SEARCHES
Unofficial terms that are not Library of Congress official terms but may be helpful