Although history students--especially graduate students--are often encouraged to find topics in which they can conduct "new" research, a class project generally requires that there be at least a minimal amount of existing scholarship. As Robert Williams observes, "If the topic is significant, there should be some secondary sources by other historians on the same topic" (52).
Remember that some literature may be tangentially relevant: in other words, it might not address your exact question from your exact angle, but it may address the same question from a different angle, or it may address a different question which has bearing on a certain part of your question.
Such sources can be important contributors to your research, especially when there is very little existing scholarship that speaks directly to your question.
How broad or narrow your search terms are, and how many or how few of them you search for at a time, will affect your discovery of these tangentially relevant sources. Step back and search a little broader to locate them.
Note also the topic's historiography, that is, "how historians' interpretations of it have developed and changed. Who has written what on the topic? When? ... How have they framed the topic and the question...? How has each secondary source used and taken account of (or taken issue with) previous sources? What different schools of thought on the topic/question exist?" (Williams 53).
Williams, Robert C. The Historian's Toolbox: A Student's Guide to the Theory and Craft of History. Second ed. Armonk, NY: M. E. Sharpe, 2007.