There are many online sources for Civil War unit histories and related materials. These consist of freely accessible digitized versions of original printed materials in the public domain, freely accessible materials that were born as digital sources, and materials that were born as digital sources but are restricted to subscribers for a fee. Freely accessible digitized older printed materials can be found at online archiving sites as Hathi Trust External, and Internet Archive External. Examples of these materials found in the Library of Congress Online Catalog will often have a link to the Hathi Trust or Internet Archive digital version. Online projects sponsored by institutions of higher learning include Making of America External and Perseus Digital Library External. State sponsored projects are additional sources for Civil War related unit materials, and are usually specific to a given state. Examples below include Alabama, Illinois, New York and Texas.
The subscription resources marked with a padlock are available to researchers on-site at the Library of Congress. If you are unable to visit the Library, you may be able to access these resources through your local public or academic library.