ArchiveGrid
Find over 7 million records for archival materials at over 1,400 archives, libraries, historical societies, and museums. These materials include historical documents, personal papers, family histories, and other archival materials. Most of these materials are located at archives in the United States. For materials in European archives, see Archives Portal Europe. You can also search for institutions based on geographic location.
Archives Portal Europe
Search for archival collections about the history of Europe and collections held at European institutions about the rest of the world. The Portal provides access to over 280 million archival descriptive units held in more than 7,000 archival institutions in more than 30 countries.
WorldCat
The most comprehensive database of information about library collections, including general resources to inform your research as well as rare and unique items such as rare books, manuscripts, archival collections, and much more. Because of the amount of information this database contains, it can be overwhelming to search. Worldcat provides some tips to narrow your search down. The search box on the main page is good to get a general idea about all the different types of resources for your topic, but when you want to focus on your specific topic, use the advanced search (click on the slider icon to the right of the search box and the advanced search box will pop up).
American Historical Association's Archival Wiki
This site provides listings of archives throughout the world, subdivided by country. This listing includes contact information, holdings, access policies, and other pertinent information.
ArchivesHub
Locate unique sources held at over 220 institutions in the United Kingdom.
Consortium of European Research Libraries Portal (CERL Portal)
The CERL Portal gives access to descriptions of manuscripts of all periods and early printed materials (up to 1830) in collections in Europe, the United States and Australia.
Discovery
Find records from the National Archives and over 2,500 other archives in the United Kingdom.
National Register of Archives
A comprehensive catalogue compiled from English and Scottish Archives that contains information about the nature and location of manuscripts relating to British History. This is the best resource to begin with for archival resources related to British History.
Social Networks and Archival Contexts (SNAC)
Find biographical and historical information about persons, families, and organizations that created or are documented in historical resources. In addition you can locate archival collections and related resources at repositories in the US and around the world.