Ammishaddai Moore, Jr., was born on May 30, 1846, in Upton, Virginia, to Ammishaddai and Mary Moore. His father was a farmer who owned $17,000 of real estate and $9,500 of personal property by 1860. He grew up in Clarke County, Virginia.
He enlisted in the Confederate army on July 25, 1862, and he mustered in as a private in Company D of the 6th Virginia Cavalry later that day. The regiment took part in the Second Battle of Bull Run, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, the Overland Campaign, the siege of Petersburg, and the Appomattox campaign.
He was hospitalized with bronchitis in Charlottesville, Virginia, in January 1864, but he eventually recovered and rejoined the regiment. Union forces captured him near Yellow Tavern, Virginia, on May 11, 1864, and they imprisoned him at Point Lookout, Maryland. He reportedly escaped while en route to Elmira, New York. He returned to his regiment, and he remained in the army until at least March 1865.
Moore returned to Clarke County after the war, and he married Annie B. Cabell. They had at least nine children: William Cabell, born around 1879; Mary, born around 1880; Annie, born around 1882; Margaret, born around 1884; Joseph, born around 1887; Elvira, born around 1888; Charles, born around 1891; John, born around 1894; and Elizabeth, born around 1896. He worked as a lawyer. He remained in Clarke County for the rest of his life, and he died of bronchial pneumonia in Berryville, Virginia, on January 18, 1929.