William A. Mulkey was born around 1830 in Washington, D.C. During the Civil War, he served as a surgeon in the 3rd Confederate Cavalry. Union forces captured him on August 15, 1864, near Dalton, Georgia. They imprisoned him at Camp Chase in Ohio. He remained imprisoned until at least January 6, 1865.
He settled in Rutherford County, Tennessee, after the war. He married Geneveve Smith on April 28, 1866, and they had at least five children: Anna, born around 1867; George, born around 1869; James, born around 1872; William, born around 1875; and Albert, born around 1878. He worked as a physician, and by 1870, he owned $7,000 of real estate and $1,500 of personal property. He moved to Kaufman, Texas, in the 1870s, and he died there on January 23, 1897.