The Civil War had a major impact on literature during this time period. The horrors of the war shook people up and created a more pessimistic outlook on life. This was one of the first wars that was photographed so people had images to look at even if they were not involved in the war itself. The saying "a picture is worth a thousand words" is definitely applicable in ths case.
Realism came into play in large part out of need as a result of the war. People had something to write about but did not at the time have the right "tool" to do it. Realism/realistic novel was that tool. Romanticism, which came before realism, did not lend itself to write about the new perspective of society post Civil War.
The first sentence is your best choice.
Because it is not the actual word
