The 19th Indiana was raised at Indianapolis, Indiana on July 29, 1861. It saw severe fighting in the 1862 Northern Virginia Campaign. In their first battle at Gainesville, the 19th supported the left flank of the embattled 2nd Wisconsin, fighting Confederates near the buildings of John Brawner's Farm. They also fought in the main part of the Second Battle of Bull Run, where they, along with the rest of the Iron Brigade, were part of the rear guard covering the retreat of Union Army General John Pope. During the subsequent Maryland Campaign, the 19th attacked Turner's Gap in the Battle of South Mountain, and then suffered considerable casualties battling Hood's Texas Brigade in the D.R. Miller cornfield at Antietam.
During the first day of the Battle of Gettysburg on July 1, 1863, the 19th pushed a part of James J. Archer's Confederate brigade off McPherson's Ridge, and then stubbornly defended the heights later in the day before withdrawing to Seminary Ridge. When the I Corps retreated to Cemetery Hill, the Iron Brigade and the 19th Indiana were sent over to nearby Culp's Hill, where they entrenched. They saw comparatively little action the rest of the battle. The regiment later served that year in the Bristoe and Mine Run Campaigns and in 1864 during the Overland Campaign and the Siege of Petersburg.
The regiment was amalgamated with the 20th Indiana Infantry on October 18, 1864.
