John Mercer Brockenbrough was born August 1st 1830 in Richmond County, Virginia, the son of Moore Fauntleroy and Sarah Waller (Smith) Brockenbrough. He attended and graduated from the Virginia Military Institute in 1850.
Brockenbrough was appointed the Colonel of the 40th Virginia at the start of the Civil War. They were a part of Confederate Major General A P Hill’s Light Division. Brockenbrough led his men during the Seven Days Battles seeing casualties of about 50%. At the Battle of Chantilly he moved up to Brigade command, and continued there through the battles of Harpers Ferry, Sharpsburg, and Fredericksburg. In the early part of the 1863 Confederate Brigadier General Henry Heth replaced Brockenbrough as the brigade commander. But, when A P Hill was wounded at the Battle of Chancellorsville, Heth moved up and Brockenbrough got his brigade back. His men saw action at Gettysburg on the afternoon of July 1st 1863, fighting against Union Colonel Roy Stone’s Pennsylvania Buck Tails, and as part of Pickett’s Charge on the 3rd.
Following a reckless charge on Union troops at the Battle of Falling Waters on July 14th 1863; a part of the Confederate retreat from Gettysburg, Brockenbrough was removed from Brigade command and he resumed command of the 40th Virginia. He led the 40th the Battles of Bristoe and Mine Run, before resigning his command January 21st 1864 still as a Colonel.
Brockenbrough lived in Norfolk and Richmond, Virginia following the war. He died August 25th 1892 in Richmond, Virginia and is buried in the Hollywood Cemetery there.