William Marion Riddle was born on February 23, 1836, in South Carolina to William Riddle. His father was a farmer who owned $900 of real estate by 1850. He grew up in Laurens District, South Carolina, and he married a woman named Pernecy. They had at least ten children: Susan, born around 1858; William, born around 1860; Franklin, born around 1862; Rebecca, born around 1866; Lou, born around 1866; Lonar, born around 1872; Lee, born around 1873; Buford, born around 1875; James, born around 1877; and Marvin, born around 1879.
He enlisted in the Confederate army on January 25, 1862, and he mustered in as a private in Company E of the 3rd South Carolina Infantry Battalion. He was promoted to corporal sometime in 1862. The regiment took part in the Second Battle of Manassas, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, the Battle of Chickamauga, and the Overland Campaign. He was wounded near North Anna, Virginia, on May 23, 1864, and Confederate officials sent him to South Carolina to recover.
He settled in Youngs, South Carolina, after the war, and he earned a living as a farmer. By 1870, he owned $1,000 of real estate and $200 of personal property. He died on July 19, 1886.