The Digital Public Library of America (DPLA) provides freely available resources from America’s libraries, archives, and museums. You can find many primary sources here from different time periods and on different subjects. Go to their Primary Source Sets to either search or browse sources by topic.
See DPLA's help page for more information on how to search and browse the collection.
DPLA's Primary Source Sets are designed to help students develop critical thinking skills by exploring topics in history, literature, and culture through primary sources. Drawing online materials from libraries, archives, and museums across the United States, the sets use letters, photographs, posters, oral histories, video clips, sheet music, and more. Each set includes a topic overview, ten to fifteen primary sources, links to related resources, and a teaching guide.
HathiTrust is an online collection of books published before 1923. Many of these can be viewed online in their entirety, and others can be searched for keywords.
This guide provides an introduction to the HathiTrust Research Center and its research tools.
The Wayback Machine has archived billions web pages from 1996 to the present and lets you view old versions of websites, even those that no longer exist. The Wayback Machine is part of the Internet Archive, which is a non-profit library of millions of free books, movies, software, music, websites, and more.
Europeana is a European digital library which gives access to online collections of many Europeans institutions (archives, libraries, museums). You can search the catalog for newspapers by title or by period.