Lewis A. Armistead nearly scuttled his military career when he broke a plate over the head of fellow cadet Jubal A. Early and was expelled from West Point. He was, however, commissioned directly into the infantry in 1839 and served in the Mexican War, being wounded at Chapultepec and earning two brevets. He resigned his captaincy on May 26, 1861, and headed back east to offer his services to the Confederacy.

His assignments included: major, Infantry (from March 16, 186 1); colonel, 57th Virginia (September 23, 1861); brigadier general, CSA (April 1, 1862); commanding brigade, Department of Norfolk (ca. April 1-12, 1862); commanding brigade, Huger's Division, Department of Northern Virginia (April 12-July 1862); commanding brigade, Anderson's Division, lst Corps, Army of Northern Virginia July-September 17, 1862); and commanding brigade, Pickett's Division, in 1st Corps, Army of Northern Virginia (October 1862-February 25, 1863 and May-July 3, 1863), in the Department of Virginia and North Carolina (February 25-April 1, 1863), and in the Department of Southern Virginia (April 1-May 1863).

After serving in western Virginia, he was given command of a brigade in the Norfolk area and later served with it on the Peninsula, seeing action at Seven Pines and in the Seven Days. He fought at 2nd Bull Run and Antietam, where he was wounded. After being lightly engaged at Fredericksburg, he went to southeastern Virginia, his home state, with Longstreet. Returning for the invasion of Pennsylvania, he fell mortally wounded among the guns of Cushing's Battery during Pickett's Charge at Gettysburg. He died two days later in Union hands.