You may find it useful to use a published guide to find a resource or an archive. Here are some of the main tools for finding archives, located in DePaul's Reference Collection. You can find more print guides like these by searching in the catalog. Use the term catalogs in your search.
The main online tools for locating archival collections are listed below. While these guides are online, the sources themselves are not. Search these databases to find descriptions of materials held in archives and special collections around the world.
Sometimes the only way to find a document is to make a special trip to an archive.
For more advice on what to expect when visiting an archive, read this Survival Guide to Archival Research from the American Historical Association.