Brackman, Barbara. Quilts From the Civil War. Lafayette: C&T Publishing, 1997.
Ramsey, Bets, and Merikay Waldvogel. Southern Quilts: Surviving Relics in the Civil War. Nashville: Rutledge Hill Press, 1998.
Several books deal with Friendship quilts. I like this one best:
Lipsett, Linda Otto. Remember Me: Women and Their Friendship Quilts. San Francisco: Quilt Digest Press, 1985.
These are the general reference books I consulted most often:
Ferrero, Pat, Elaine Hedges, and Julie Silber. Hearts and Hands: The Influence of Women and Quilts on American Society. San Francisco: Quilt Digest Press, 1987.
Houck, Carter. The Quilt Encyclopedia Illustrated. New York: Harry N. Abrams, 1991.
Kiracofe, Roderick. The American Quilt: A History of Cloth and Comfort, 1750-1950. New York: Clarkson Potter, 1993.
Orlofsky, Patsy and Myron. Quilts in America. New York: McGraw-Hill, Inc., 1974.