I promised to give an example of a park historian doing real history, as opposed to recapitulating the shallow stuff cranked out by bestselling storytellers.
Timothy J. Reese is an independent battlefield guide specializing in the battle at Crampton's Gap, near his Burkittsville home. He began researching the fight in 1985 and distilled his findings into a remarkable 1998 book: Sealed With Their Lives: The Battle for Crampton' s Gap. The study is as much a product of thinking as walking.
Author Reese has a totally unexpected and refreshing view not only of Crampton's Gap but of the Maryland Campaign in general and he regards the battle at the Gap as the key to understanding the whole. Antietam was not supposed to happen; Crampton's Gap was to be the engine for undoing Lee once McClellan found Lee's special orders. Reese's interpretation of McClellan's envisioned battle is marvelous and his "deconstruction" of Mac's orders to Corps Commander Franklin are unsurpassed. I feel I would spoil the fun for any deep students of the war, were I to give away more.
This is a wonderful artifact by a battlefield guide (independent!) who searched for truth in a cluttered, worked over corner of Civil War history. It is pricey, but its freshness and rareness make it worth the cost to obtain it.
Now you might say independent (self-appointed) guides and experts are not park historians, per se. You'd be right. But there is no Crampton's Gap park with an assigned official park historian, is there? And where is there an historian this good in park uniform, anyway...