The First Vermont Brigade, or "Old Brigade" was an infantry brigade in the Union Army of the Potomac during the American Civil War. It suffered the highest casualty count of any brigade in the history of the United States Army, with some 1,172 killed in action. It was the only brigade in the Army of the Potomac known by the name of its state.
The "Old Brigade" served from 1861 to 1865 and was one of two brigades from Vermont, both famous in their own right.
The First Vermont Brigade was organized in October 1861, primarily through the efforts of Maj. Gen. William F. "Baldy" Smith. It was composed of the 2nd, 3rd, 4th, 5th and 6th Vermont Infantry regiments, which had been individually mustered into service between June and September, for a time, it also included the 26th New Jersey Infantry. Its first commander was Brig. Gen. William T. H. Brooks. In April 1862, the brigade was incorporated into the Army of the Potomac as the 2nd Brigade, 2nd Division, VI Corps, and first saw action during Maj. Gen. George B. McClellan's Peninsula Campaign in the battles of Williamsburg and Savage's Station. It later was present at Antietam and Fredericksburg. Under the command of Brig. Gen. Lewis A. Grant, the Vermonters fought in the campaign culminating in the Chancellorsville. The Vermonters participated in VI Corps' capture of Marye's Heights in the Second Battle of Fredericksburg and then were prominent in the fighting at Salem Church. They were held in reserve during the Battle of Gettysburg, holding a flank guard position behind Big Round Top, losing only one man wounded. After the Gettysburg Campaign, elements of the Vermont Brigade were sent to help quell the draft riots in New York City.