Many of the Rangers at the 150th of Sharpsburg/Antietam were from other battlefields and lending a hand due to the large number of visitors. Although most were well versed in the events of the battle, when you got down to the regiment level in a discussion, not all of the Rangers knew specific details. I went on one of the 90 minute tours with Ed Bearss - Mumma Farm to Sunken Road - he gives details! He's still got it at 89.