During the Confederate Army of Northern Virginia’s invasion of Maryland in June 1863, the Army of the Potomac moved north in pursuit. On Monday, June 29, Gen. John F. Reynolds’ I Corps, leading the Union advance with 15,000 men, 2,900 horses and mules, and 475 wagons, marched through Lewistown on a rainy day while traveling from west of Frederick to Emmitsburg on an eighteen-mile march toward Gettysburg, Pennsylvania. This was the halfway point. When the armies fought on July 1, the troops that passed here were the first engaged. The Iron Brigade, made up of the 19th Indiana and the 2nd, 6th, and 7th Wisconsin, was decimated on the ridges west of Gettysburg but held the Confederates at bay. After Reynolds was killed about 10:30 that morning, Gen. Abner Doubleday took command. On July 7, after the battle, the army’s I, VI, and XI Corps passed here heading south; the I and VI Corps then turned west and crossed Catoctin Mountain into the Middletown Valley at Hamburg Pass, while the XI Corps continued down the Emmitsburg Road to Frederick. The Iron Brigade had been formed in autumn 1861 from the 2nd, 6th, and 7th Wisconsin and the 19th Indiana Infantry Regiments, with the 24th Michigan added a year later. Gen. Joseph Hooker called it his “iron brigade” after heavy losses at the Battle of South Mountain on September 14, 1862, and the name remained. Its black-hatted soldiers deployed early at Gettysburg on July 1, 1863, to stop the Confederate advance, but several regiments suffered between 65 and 80 percent casualties, effectively destroying the brigade.