These tools can be used to identify publications pre-dating the 1976 start of the online Catalog of Government Publications.
1895-June 1976 and earlier volumes are shelved in the Depository Collections on Level 2 area: GP 3.8:
Basic, multipurpose catalog/index, listing thousands of publications each year. Indexing by subject, author, some keywords, SuDocs call number, etc.
REF Z 1223.A182 (Volume 1 not available)
Commercially-published index to subject listings in the Monthly Catalog, dating from 1900 to 1971, providing references to Monthly Catalog listings.
REF J 83.L47 1979
Commercially-published listing of titles, dating from 1789 to 1976, providing SuDocs numbers and publication dates.
This resource listed Federal Government publications dating from 1789-1909, effectively serving as a predecessor of the Monthly Catalog.
Texts of selected historical Congressional publications.