Situated between Biscuit Mountain on the south and Mother Leathercoat Mountain to the north, Thoroughfare Gap was the site of several Civil War engagements, the most significant on August 28, 1862, when a Confederate victory demonstrated the strategic importance of the gap and rail line. Federal soldiers occupied the gap frequently throughout the war, yet despite Union surveillance, Col. John S. Mosby and his partisans often camped nearby and used their familiarity with the difficult terrain to stage raids and evade capture. Chapman's (Beverly's) Mill, across I-66, played a role in the 1862 fighting and other engagements; sharpshooters from both sides used its upper windows to attack or defend the gap. Built in 1859 and enlarged to five stories in 1858, the mill was by 1864 a shell. Owner John Chapman sued the U.S. government to recover $5,194.59 for damage that rendered the mill inoperable, but the suit failed, his family committed him to an asylum, and he died in 1866. In 1870, Col. Robert Robert Beverly bought and restored the mill, which operated until 1951 before arsonists burned it in 1998.