To cite a letter contained in the papers of Caroline Howard Gilman in the collections of the South Carolina Historical Society:
Bibliography: Caroline Howard Gilman papers, South Carolina Historical Society
Note: Caroline Howard Gilman to Anna M. White, 15 January 1859, Carolina Howard Gilman Papers (1036.00), South Carolina Historical Society.
For more examples and variations of notations and bibliographic citations, please refer to the Chicago Manual of Style: Section 14.
The above examples have been taken from the Chicago Manual of Style, 16th edition, section 14.18.
The 1987 edition of the Guide to the National Archives of the United Statesoffers the following advice: “The most convenient citation for archives is one similar to that used for personal papers and other historical manuscripts. Full identification of most unpublished material usually requires giving the title and date of the item, series title (if applicable), name of the collection, and name of the depository. Except for placing the cited item first [in a note], there is no general agreement on the sequence of the remaining elements in the citation. . . . Whatever sequence is adopted, however, should be used consistently throughout the same work” (761). This advice has been extended by the leaflet Citing Records in the National Archives of the United States (available from the National Archives and Records Administration; see bibliog. 4.5), which includes advice on citing textual and nontextual records, including electronic records and digitized resources. Citations of collections consulted online (to date, a relative rarity for this type of material) will usually take the same form as citations of physical collections, aside from the addition of a URL or database name (see 14.6–18).