On the evening of July 4, 1863, one of the most confusing battles of the American Civil War unfolded at Monterey Pass along the Mason-Dixon Line. Around 9:00 p.m., Union cavalry under General Judson Kilpatrick came into contact with the Confederate 1st Maryland Cavalry, Company B, under Captain George Emack, whose small detail guarded the approach to the pass with support from one cannon of Captain William Tanner’s Battery. In darkness and a blinding thunderstorm, Confederate artillery opened fire, and after the confusion briefly cleared, the Confederates charged and pushed Kilpatrick back before falling back to Red Run, where fighting continued for several hours between flashes of lightning and muzzle fire. The battle spread to Fairfield Gap and Leitersburg, Maryland. By 3:30 a.m. on July 5, the Union cavalry had reached the turnpike where the Confederate wagon train was located, capturing and destroying seven miles worth of wagons and taking 1,000 prisoners as they moved toward Ringgold, Maryland. At Leitersburg, another two miles worth of wagons were destroyed and several hundred prisoners were taken. The Union cavalry lost 100 men. By dawn, the fighting had ended, and the Confederate army continued using Monterey Pass in its retreat from Gettysburg, while the Union cavalry moved to Smithsburg, Maryland, where Confederate General J.E.B. Stuart attacked them, and then fell back to Boonsboro, Maryland, arriving shortly after midnight on July 6, 1863.