Unit or regimental histories are compiled either by members of that unit, historians of veterans' associations, or other interested parties. Information collected in the histories may include the soldiers of the units, where the unit served in the war, descriptions of the battles in which the unit participated, and muster rolls. Military histories help bring your ancestor's experiences to life, providing details that make it easier to understand the events and circumstances that your relative endured. Learning who your ancestor served with may also lead to the discovery of journals or letters by his fellow soldiers that can add still more detail. State archives, major libraries, lineage societies, and military historical organizations are all good sources for regimental or unit histories.