These indexes can be helpful for locating older (pre-1976) government publications.
Monthly Catalog of U.S. Government Publications, 1895-1976
Lv.1-Documents Reference: GP 3.8: (1895-1976)
Index to the publications of the U.S. Government. Gives the call number necessary to find the publications on the shelves. New documents are cataloged in the Catalog of Government Publications.
Cumulative Subject Index, 1895-1899, and 1900-1971
Lv.1-Documents Reference: 15.73 X C9711 or GP 3.8:
Citations given under the subject refer to the year of the Monthly Catalog and the appropriate page number or item number in the Monthly Catalog.
Cumulative Title Index, 1789-1976
Lv.1-Documents Reference: 015.73 X L642c
This index gives the call number for older documents so it is not necessary to go back to the Monthly Catalog.
Checklist of United States Public Documents, 1789-1909
Lv.1-Documents Reference: GP 3.2:C 41/2
Lv.1-Documents Reference: GP 3.6: (1889-1940)
Excellent document index for older publications.
A Descriptive Catalogue of the Government Publications of the United States, Sept. 5, 1774-March 4, 1881 (Poore's Index)
Lv. 1-Documents Reference: Y 4.P 93/1:G 74/1
This is a classic index for early government information. It is structured chronologically and includes an index.
Document of the Day from the National Archives
Federal government information is still making its way online. Recent reports are often available online, but historical materials are slowly being digitized by agencies, libraries, and corporate vendors. The majority of historic government information is available in print at this time.
Tracking down older government information can be challenging (but worthwhile). Items from 1976-present should be in the library catalog. The library is working on getting records for all of its government documents in the catalog, but it will take time to get 200 years worth of material in the catalog. If there isn't a record for the item you want in the catalog, the library may still own it; remember the 1976-present limitation. Try WorldCat, the digital Serial Set, or some of the print indexes to track down a call number.
You can always ask the Government Documents librarian for help in finding a government report. This is what we're here for.