This multi-volume set was published over the course of 21 years. It was organized into four “series.”
Series I consists of 53 volumes, and compiles the formal reports of the Union and Confederate armies of all military field operations, including related correspondence, orders, and returns of operations.
The 8 volumes of Series II contain all Union and Confederate reports, correspondence, orders, and returns pertaining to prisoners of war.
The 5 volumes of Series III contains all correspondence, orders, reports and returns of Union authorities not specifically included in the two previous series, such as annual and special reports of the Secretary of War and the General-in-Chief.
Series IV consists of 3 volumes that contain records of Confederate authorities.
Each volume has its own index in the back; there is also a General Index to all the Series combined. The best approach is to use the General Index to identify which Series and volumes contain information on a topic. For example, the following entry in the General Index,
“Appomattox Campaign, I, 46,47,51”
indicates that material on the Appomattox Campaign can be found in Series I, volumes 46, 47, and 51.
The next step is to go to the indexes in the back of each volume to find the page numbers where the information may be found. Continuing the example, the indexes in the back of volumes 46,47, and 51 will give the page numbers for materials on the Appomattox Campaign within each volume.
In the hundred years since the last of the Official Records was published by the U.S. government, additional primary source documents pertaining to the Civil War were discovered. These previously lost or omitted documents have been published as a supplement to the original set of records.
The organization and numbering of the Supplement volumes correspond to that of the original Official Records. Although produced by a private publisher, the contents of the Supplement are primary source government documents.
Volumes 11 and 12 are the indexes to the first ten volumes of the set, which comprise Series I. There is also a five-part index to Series I, II, and III volumes combined. In the combined index, the entries refer to Serial numbers (not volume numbers) and page numbers. The Serial numbers are found on the title pages of the volumes.