Your original question: >>> I am curious where they got the information that Col Vandeventer was one of the Immortal 600. <<<

I don't know. Colonel Vandeventer's Compiled Military Service Records clearly state that he was delivered to Confederate authorites on 3 AUG 1864 at Charleston, South Carolina. And that is consistent with other records of the First Fifty.

I hope this helps!

Hugh Simmons
Fort Delaware Society
Website: www.fortdelaware.org
E-mail: society@fortdelaware.org