Statistics for occurrence #1 of “Chester Gap” in chapter 4 of The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 3: The Decisive Battles.:

...d to continue his retreat up the Shenandoah until Longstreet, sent in advance with part of his command, had so blocked the Federal pursuit that most of the Confederate army was able to emerge through Chester Gap and move to Culpeper Court House. Ewell marched through Thornton's Gap and by the 4th of August practically the whole Army of Northern Virginia was south of the Rapidan, prepared to dispute the cro...
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Entity Corpus Doc Corpus Doc  
Chester Gap (Virginia, United States) 337 2 5 0 0 user votes

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