"This plan for the organization of the Inventory is as follows: Series I consists of reports on the administration of the survey, acknowledgments, and general discussions of the location, condition and content of federal archives in the states. Succeeding series contain the detailed information secured by workers of the survey, in inventory form, a separate series number being assigned to each of the executive departments (except the Department of State) and other major units of the federal government. Within each series no. 1 is a general introduction to the field organization and records of the governmental agency concerned; the succeeding numbers contain the inventory proper, separate numbers being assigned to each state in the alphabetical order. Thus, in each series, the inventory for Alabama is no. 2, and for Arizona no. 3, that for Arkansas no. 4, etc." --Pref., Series II, no. 3.
Within each series, some numbers are issued by the Historical Records Survey, some by the National Archives Project, and some by the Survey of Federal Archives.
Series numbers have been assigned as follows: II. Federal Courts, III. Department of the Treasury, IV. Department of War, V. Department of Justice, VI. Post Office Department, VII. Department of the Navy, VIII. Department of the Interior, IX. Department of Agriculture, X. Department of Commerce, XI. Department of Labor, XII. Veterans' Administration, XIII. Federal Civil Works Administration, XIV. Emergency Relief Administration, XV. Works Progress Administration, XVI. Farm Credit Administration and XVII. Miscellaneous agencies.