Chicago (Turabian) style is the most frequently used style for the discipline of history. It allows you to use either footnote or parenthetical author-year citation -- ask your professor which (s)he prefers. There is a brief online guide to citation using the Chicago style at the University of Wisconsin Writing Center.
Ellis Library also has a copy of the latest edition of the guide at Ready Reference Z253.U69.
Zotero is a free, open access, downloadable program that can format your citations for you. For this class, set it to Chicago Full Note style.
