William D. Kirkpatrick was born around 1842 in Chester, South Carolina, to Hezekiah Kirkpatrick. His father was a blacksmith who owned $1,200 of real estate and $14,000 of personal property by 1860. The family moved to Monroe County, Mississippi, in the 1840s and then to Lowndes County, Mississippi, in the 1850s. By 1860, Kirkpatrick was working as a farm laborer.
He enlisted in the Confederate army on August 1, 1861, and he mustered in as a private in Company D of the 24th Mississippi Infantry on October 11. According to his service records, he was 5 feet, 7 inches tall, with light hair and grey eyes. He eventually earned a promotion to corporal. He died on October 8, 1862.