Jimmy Stewart is the man.
He really was. He was always convincing, and never had the propensity to overact that some actors of the time had. His characters are 100% believable.
Not to mention It's A Wonderful Life, Anatomy of a Murder, Vertigo, Rear Window, and most importantly Mr. Smith Goes to Washington are among the greatest American Classics.
Never seen Shenandoah--I'll put it in my Netflix queue, soon as I get Mad Max 2.