Any research project on the military dimensions of the Civil War must rely on the O.R.
This extensive collection of printed primary source documents, titled collectively The War of the Rebellion: a Compilation of the Official Records of the Union and Confederate Armies, and known to historians simply as the "O.R", is the principal body of official orders and correspondence that document the course of military operations in all theaters of the American Civil War. It is essential for researchers in Civil War history, and learning bout its value and use is a fundamental aspect of learning about the military history of the conflict
There are multiple ways to access it. Several online versions of the entire O.R. are available:
This online version of the O.R., offered by Ohio State University, provides just a simple single-search box that searches across all volumes of the entire O.R. When searching by a commonly-occurring name of a person (e.g. "Grant") or a very commonly-occurring name of a place "Shiloh" it may return too many results to be helpful. On the other hand, this kind of search capability can at times be useful when search terms are very distinctive, such as a person's name or a place-name that is very distinctive and uncommon. Example: David A. Enyart, commander of the 1st Kentucky Infantry. Because "Enyart" is not a very common last name, searching by that name may yield relevant results near the top of the results list because even across the whole O.R. that name is uncommon enough that it will occur only a few times, unlike a common name like "Grant".
E-book versions of the O.R. are available through the Hathi Trust Digital Library, Google Books, and Internet Archive.
The organization of the various reports related to the action of Shiloh within this volume can require some getting used to on the part of the researcher. The editors of the O.R. grouped reports in more or less according to the sequence of the overall order of battle of each side, presenting first all the Union reports and then all the Confederate reports A listing of Union and Confederate reports is found pages 93-98 of Ser. I, Vol. X, Pt. 1, cited above. Users may think of this as a partial table of contents of sorts. It does not, however, list the page numbers for each report within that volume but just simply shows which number it is in the sequence of reports. A user can use that sequencing, nevertheless, to locate a desired report. Note that if one is studying the action of a particular unit, reports besides the one written by that unit's commander may indeed be relevant. Even a brief survey of O.R. reports will reveal that commanders often referred to units adjacent to them in the line or by whose action they were otherwise affected. Likewise, the reports of a division commander or brigade commander might refer to specific brigades or regiments, respectively, under their command.
Researchers should note that although the above volume does contain many reports from units engaged at Shiloh, some material relevant to Shiloh may be found in other parts of the O.R. and therefore cadets may need to consult other volumes.
Print copies are available in the Jefferson Hall 3rd Floor Reading Room and the History Department Library collection.