Pennsylvania is the only northern state known to have a list of conscientious objectors, men who refused military service due to religious beliefs. Many of these objectors were from the Quaker, Mennonite (and Amish), and Dunkard churches. If you have ancestors in your family tree who were of age during the war but did not serve, perhaps they were one of the many objectors. You can search for relatives at the Genealogical Society of Pennsylvania’s, Conscientious Objectors database.
The list is broken down into alphabetical groups and clicking on a list, opens it in a PDF type format. You can search the list using Ctrl+f.
Conscientious objectors didn’t get off free. They had to pay $300 or an equivalent service. Many would say that was a small sacrifice, all things considered. Approximately 3,211,067 soldiers fought in the war. Of those, it is estimated that 620,000 died from combat, accident, or disease. To give a visual of the Civil War compared to others, consider this bar graph:
Gettysburg was the bloodiest battle of the war with an estimated 51,000 casualties. Most of the dead were buried on the battlefields, others buried at the hospital where they succumbed. At most battlefields, the dead were exhumed and moved to National or Confederate cemeteries, however, there are undoubtedly thousands if not tens of thousands of Civil War soldiers in unknown battlefield graves.