The Civil War Trust is the largest battlefield preservation organization in the United States, and its website contains links to dozens of other Civil War-related sites, including the National Park Service Home Page (which includes separate pages for 22 Civil War battlefield sites, parks, and memorials), the United States Civil War Center, the Library of Congress American Memory Page, and the American Battlefield Protection Program.
The Valley of the Shadow Online Database (Virginia Center for Digital History)
This website tells the story of the struggles of two communities, one Northern and one Southern. It includes primary documents from the Civil War era.
A Companion to the Civil War and Reconstruction edited by Lacey Ford (Wiley-Blackwell)
A People's Contest: The Union and the Civil War 1861–1865 by Phillip Shaw Paludan (University Press of Kansas)
Battle Cry of Freedom: The Civil War Era by James M. McPherson (Ballantine Books)
Daughters of the Union by Nina Silber (Harvard University Press)
Don't Know Much about the Civil War by Kenneth C. Davis (William Morrow & Company)
Forever Free: The Story of Emancipation and Reconstruction by Eric Foner (Vintage Publications)
In the Presence of Mine Enemies: The Civil War in the Heart of America, 1859–1863 by Edward L. Ayers (W. W. Norton & Company)
Major Problems in the Civil War and Reconstruction, 2nd Edition edited by Michael Perman (Houghton Mifflin Company)
Mr. Lincoln's Camera Man: Mathew B. Brady, Revised 2nd Edition by Roy Meredith (Dover Publications)
Reconstruction: America's Unfinished Revolution, 1863–1877 by Eric Foner (Harper Perennial Modern Classics)
Scarlett Doesn't Live Here Anymore by Laura F. Edwards (University of Illinois Press)
The Civil War by Ken Burns (PBS Video)
The Civil War: A Narrative (3 Volume Set) by Shelby Foote (Vintage Books)
The Civil War: An Illustrated History by Geoffrey C. Ward, and Ric and Ken Burns (Knopf Publications)
The Civil War and Reconstruction: An Eyewitness History by Joe H.
Kirchberger (Facts on File)
The Life of Johnny Reb: The Common Soldier of the Confederacy by Bell Irvin Wiley (Louisiana State University Press)
The Life of Billy Yank: The Common Soldier of the Union by Bell Irvin Wiley (Louisiana State University Press)
The Negro's Civil War by James M. McPherson (Ballantine Books)