A historiography is a survey of the historical research conducted on a certain topic, for example the history of midwifery in the United States. Historiography is often called "the history of history," because they assess what research has been conducted on the topic, what was said and how primary sources were analyzed, and how certain arguments compare and contrast to one another within the broader context of the scholarly record.
To use our example above, a historiography of the history of midwifery in the United States would discuss which historians have researched midwifery in the US, what analytical lens did they use, what argument did they make, and how their argument sits against others' and in the scope of the research on the topic.
The purpose of a historiography is to discuss the research conducted by other historians on the topic, not to perform original research or commentary on the subject itself.
You are creating a survey of the research that has been conducted on a topic, so you will, of course, need to discover and become familiar with the notable scholars and arguments on that topic. There are a couple strategies you can use to find these figures and perspectives:
As you search for and collect resources related to your topic, make note of common themes or analyses that the scholar's are making. A historiography should not only identify the prominent scholars and arguments on a topic - they need to set those arguments in context with each other and with scholarly trends over time.
Once you have pinpointed the approach and type of history, you can then compare and contrast with your sources:
When you have found commonalities in perspective, approach, or type, then you can use these to help organize your paper.
Examples of Historiographies