America's Reconstruction: People and Politics after the Civil War - University of Houston - Part of the "digital history" site that contains primary sources on slavery, United States, Mexican American and Native American history.
Civil War and Reconstruction - Library of Congress - This exhibition contains succinct overviews of several aspects of the Civil War and Reconstruction and features primary sources, maps, and images.
Digital Public Library - "DPLA offers a single point of access to millions of items from libraries, archives, and museums around the United States." The DPLA portal allows you to search digital collections from institutions and organizations such as Hathi Trust, Internet Archive, the Smithsonian, the National Archives, Boston Public Library and more.
Freedmen's Bureau Online - Contains articles, records and images related to the Freedmen's Bureau.
Harper's Weekly: Toward Racial Equality - Harper's Weekly - Materials from the magazine are presented in order to give a true historical picture of the leading 19th-century newspaper's view of black Americans.
HathiTrust Digital Library - HathiTrust is a partnership of academic libraries and research institutions that have come together to build and share a digital repository of print works. The HathiTrust Digital Library has "more than 10 million volumes, making it one of the largest research library collections in the world. Over 3 miillion of these volumes are in the public domain and fully viewable online."
Internet Archive - The Internet Archive hosts one of the largest collections of freely available digital content on the Web and includes digitized print books, audio files, moving images and, by means of the Wayback Machine, cached copies of websites.
Teddy Roosevelt Papers - Library of Congress -- The papers of Theodore Roosevelt (1858-1919), public official, author, decorated veteran of the Spanish-American War, governor of New York, and president of the United States (1901-1909), consist of approximately 276,000 documents (roughly 461,000 images), most of which were digitized from 485 reels of previously reproduced microfilm. Held in the Library of Congress Manuscript Division, these papers constitute the largest collection of original Roosevelt documents in the world. The collection contains personal, family, and official correspondence, diaries, book drafts, articles, speeches, and scrapbooks, dating from 1759 to 1993 with the bulk of material from the period between 1878 and 1919.