When we think of Westerns we generally think of the Southwestern desert, but at the time of the Civil War, large parts of even the Eastern United States were farmland (a lot of it still is today), and so all the standard 'Western' tropes fit easily into tales from this earlier period in U.S. history.
Shenandoah is part of the last wave of great Technicolor epics, and a "western" after it's own fashion. Jimmy Stewart plays Charlie Anderson, father of several boys and a daughter, and the patriarch of a Virginia farm family. He has no desire to take up arms for either the Union or the Confederacy. His adamant refusal to get involved is increasingly tested as both sides make overtures and threats to him and his family. Finally, when his youngest son is taken prisoner by Union soldiers, he and his remaining sons take up arms to retrieve him.
Jimmy Stewart has such a wholesome image that while in this film he's still a church-going family man, hardly Josey Wales, it's entertaining to see him take on a kind of tough-guy-when-pushed role. His performance underscores the kind of 'Give Me Liberty Or Give Me Death' mentality that has resonated with Americans throughout the years, and really makes this worth seeking out.