The documentary was very good. Thanks for posting the link. For those wanting to learn more detail about the retreat, may I suggest "One Continuous Fight - The retreat from Gettysburg and the Pursuit of Lee's Army of Northern Virginia, July 4-14, 1863." The book has many good maps. Also, in back of the book it has a driving tour of Lee's retreat and the Federal pursuit. To do the tour right takes about two days.
In early June of this year, we spent several hours following parts of the retreat and the battles at Monterrey Pass, Smithburg, boonsboro, and Hagerstown. Beautiful country with many CW era homes and buildings still standing and lived in. Did not have time to make it to Falling Waters.