You will be using Chicago Style for your history essay, specifically what is called Chicago Notes-Bibliography sytem. In many of the library's subscription databases and the online catalog, the Cite tool calls it Chicago/Turabian: Humanities. If you use a citation from the library's databases make sure to use Chicago/Turabian:Humanities, and not Chicago/Turabian: Author-date.
Chicago Style: Notes-Bibliography System (Purdue OWL) - The Purdue OWL site has excellent helpful info on how to use Chicago Notes-Bibliography system in your paper. Look at their sample paper in Notes-Bibliography style to get a better idea of how your essay should look.
Notes and Bibliography Style - From the official website for Chicago Style.