ArchivesUSA is a current directory of over 5,500 repositories and over 160,790 collections of primary source material housed across the United States. Designed as a research tool, ArchivesUSA is a central collection of archival information providing descriptions of primary sources held in various kinds of repositories. This product is updated annually.

ArchivesUSA draws from three major information sources: the Directory of Archives and Manuscript Repositories in the United States (DAMRUS), the National Union Catalogue of Manuscript Collections (NUCMC), and the National Inventory of Documentary Sources in the United States (NIDS).

ArchivesUSA integrates the following information into comprehensive collection records:

• The entire collection of NUCMC (the National Union Catalog of Manuscript Collections) from 1959 to the present. NUCMC includes information gathered and indexed by the Library of Congress, covering more than 103,000 collections. Only ArchivesUSA makes all of NUCMC fully searchable in electronic form
• Names and detailed subject indexing of over 64,456 collections whose finding aids have been published separately in ProQuest UMI's microfiche series, National Inventory of Documentary Sources in the United States (NIDS)
• Collection descriptions submitted directly to us from repositories
• A growing number of more than 6,000 links to online finding aids
• Over 5,500 repositories represented
• Over 2,600 links to repository home pages.

ArchivesUSA provides information for these types of primary source material:

• Collections of original manuscript materials such as family papers, personal papers, and collections about a person or subject. This can include printed material, maps, and photographs if it is part of a larger manuscript or archival collection.
• Single item manuscripts such as diaries, logbooks, account books, or letters
• Collections of private company or government archives provided that they are regularly available to the public
• Collections consisting entirely of handwritten, typewritten, or photo-reproduced copies of manuscripts or archives
• Oral history records consisting of tapes and/or transcripts of interviews.

Undergraduates, graduate students and faculty members can use ArchivesUSA to determine whether a collection contains material useful to their work. Users can zero in relevant information by keyword searching across eight combinable search fields, including collection name, repository name, repository location and more. From any collection record, users can click to find out how to contact the repository where the collection is housed. A  Repository records provide detailed information including phone and fax numbers, hours of service, materials solicited, email and home page URLs when available. Each collection record links to its corresponding repository record, simplifying the research process.