Subject Headings are terms or phrases that best summarize the overall contents of a work and provide access to its most important topics. For this class, time and geography will provide great starting points as you define the scope of your historical inquiry. For example, if you're interested in World War I but haven't already pinpointed your topic, Library of Congress Subject Headings World War, 1914-1918--United States would be a good initial search.
You can explore LCSH on the Library of Congress website and through our catalog.