A citation is the part of your paper that tells your reader where your source information came from. This is one of the most important elements to your paper. In order to evaluate your argument, your reader must be able to consult the same sources you used. Proper citing is crucial to making a credible and persuasive argument, and to conforming to professional standards of proof.
Use the note format. Citations in history papers can take the form of footnotes or endnotes. History papers should not use the parenthetic citation style common to literature and social science papers. These do not perform the other function of footnotes and endnotes, which is to provide space to clarify your use of complex data or arguments, expand on points you believe do not merit lengthy consideration in the body of your text, and to directly address the arguments of other historians.
How footnotes work. Each time you quote a work by another author, or use the ideas of another author, you should indicate the source with a footnote. A footnote is indicated in the text of your paper by a small arabic numeral written in superscript. Each new footnote gets a new number (increment by one); do not repeat a footnote number you've already used, even if the earlier reference is to the same work. The number refers to a note number at the bottom of the page (or following the text of the paper, if you are using endnotes). This note contains the citation information for the materials you are referencing. For examples of footnotes in action, consult Rampolla ("Quoting and Documenting Sources").
What must be cited? You must acknowledge the sources of quotations, paraphrases, arguments, and specific references you may use. You need not cite sources to what most would generally consider common knowledge, like the fact that Lincoln won the Presidential election of 1860. But you must cite your source for any claim that appears to contradict common knowledge, like that Lincoln won the southern states in that election (since he wasn't even on the ballot in most southern states, this claim is controversial and must be supported). And you must cite matters of interpretation, such as an author's ideas in why Lincoln appealed to so many voters. If you are in doubt about citing "common knowledge" information, err on the side of citing; even unintended failure to cite sources constitutes technical plagiarism.
Should I use footnotes or endnotes? Either of these is fine. Most history books are now produced using endnotes, which are commonly thought to provide cleaner looking pages. Most history professors, however, prefer footnotes, so they can quickly check sources. Especially if you have a computer word-processor, which makes the task easy, you should try to use footnotes.
What should I cite?
The easiest and most important rule to remember is: when in doubt, it is better to cite a source than to not cite a source. In avoiding plagiarism, it is always wiser to choose more rather than less information.
In a research paper for history, you generally need not cite common knowledge. Common knowledge may be considered any information readily available in any encyclopedia. Common knowledge may be comprised of basic historical facts, such as dates of events and place names. For example, everyone knows that the Battle of Gettysburg occurred from July 1-3, 1863, in Gettysburg, Pennsylvania. No need to include the source of this basic information.
Arcane or debated facts of the past, however, need to be cited. These are not readily accessible facts, agreed upon by all. No one knows when exactly Jesus Christ lived, so if you include set dates for his birth and death, you need to cite the author who claims to know these things.
As this suggests, you must cite all information that constitutes another author's interpretations or arguments. Remember, the point of citation is to acknowledge the sources of ideas that are not your own, and to provide a path back through your research so other scholars can check your work. If you do not include citations, your reader cannot know where your ideas came from, and cannot check controversial statements you might make.
Matters of historical interpretation are particularly important to cite. Let's consider the Gettysburg example again. The date and place of the battle are common knowledge no one would think to dispute. But what about the argument that the Confederacy lost the battle primarily because General Longstreet failed to flank the Union forces on the left? Or that Confederate cavalry general J.E.B. Stuart was the primary cause of defeat because he failed to stay close to the Confederate army? Or that Union Colonel Joshua Lawrence Chamberlain saved the Union by protecting the Union's left flank at Little Round Top? All such claims are debatable points of interpretation. They are not facts of the past, but arguments. If you incorporate such claims by other authors in your paper, you must cite your sources.
How much to cite?
Remember to include a source citation every time you use the ideas or words of another author, either directly (through quotation) or indirectly (through paraphrase). The only exception is common factual knowledge of the variety found in encyclopedia.
Some papers, particularly those that require less argumentation and analysis on your part, are drawn almost wholly from other sources. In such instances, you might find yourself citing a source for virtually every sentence. Sometimes, it might be the same source. In these cases, it is acceptable to include one footnote for the entire paragraph. Make sure, however, that every page of the source used is referenced in the footnote. You may not do this if your information comes from several sources, or if the paragraph is interrupted by a quotation.
Before putting pen to paper (or finger to keyboard): Make sure you study your style manuals so you will avoid these common pitfalls
Guides for citing non-electronic sources
Guides for citing standard electronic sources
Online styles manuals with examples of Turabian format abound. Their quality can vary (be particularly watchful for those that do not include samples of Chicago-style citation). Here are a few reliable ones:
Consult also the library's list of style manuals at <http://library.bowdoin.edu/eref/write.shtml>
You will be using online resources, such as the CIS Masterfile, to find some of your documents. But you will be looking at them on paper. You need not cite on-line finding aids such as Lexis-Nexis or CIS Masterfile.