William G. Jackson was born around 1836, possibly in Mecklenburg County, Virginia, to Archer Jackson and Eveline F. Holmes. His father was a farmer who owned about $2,200 of real estate in 1850. Jackson married Ella F. Shaw in Mecklenburg County on February 1, 1859, and their son James was born around 1860. Jackson worked as a farmer, and by 1860, he owned $4,000 of real estate and $6,000 of personal property, including at least seven slaves.

He enlisted in the Confederate army in Mecklenburg County on June 28, 1861, and mustered in as a private in Company B of the 56^th Virginia Infantry later that day. According to his service records, he was 6 feet, 1 inch tall, with light hair and grey eyes. He mustered out on September 12, 1861, after furnishing a substitute. He rejoined the Confederate army on May 23, 1862, mustering in as a captain in Company D of the 22^nd Battalion Virginia Infantry. He was captured at Falling Waters, Maryland, on July 14, 1863. The Union army sent him to the prison camp near Sandusky, Ohio, where he remained for the rest of the war. He was released on June 11, 1865. He returned to Virginia after the war, and he died in Mecklenburg County in September 1879.