Ken Burn's films about the American Civil War have piqued my interest. Looking into it, I've found examples such as Andersonville and a fascinating lecture about Michael C. C. Adams's 'Living Hell'. I'm going to buy the book regardless but I was wondering if someone could elaborate on this war.
From the sounds of it, it was a bunch of under-trained/under-equipped young men dying of disease and malnutrition getting blown to bits in the most horrifying of ways - if they didn't die on the grueling march to the battlefield first. Adams's first-hand accounts in particular make WW1 seem tame to me.
Not to discourage other responses which might be able to more acutely answer your question, but you might be interested in this thread from a while back which explains the difference between American and European tactics at the time and how this made the American civil war particularly brutal.