Thomas Bennett Mackall was born on November 1, 1840, in Baltimore, Maryland, to Leonard and Frances Mackall. His father was a dentist who owned $15,000 of real estate and $2,000 of personal property by 1860. He grew up and attended school in Baltimore before enrolling at the University of Virginia in the late 1850s.
He sided with the Confederacy during the Civil War. He enlisted in the Confederate army on September 25, 1861, and he mustered in as a private in Company H of the 1st Maryland Infantry. According to his service records, he was 5 feet, 8 ½ inches tall, with dark brown hair and black eyes. He developed a hernia later that fall, and he received a medial discharge on November 26, 1861.
He returned to the Confederate army soon afterwards, serving as a 1st lieutenant and aide-de-camp to General William Mackall. Union forces captured him near Tiptonville, Tennessee, on April 7, 1862, during the Battle of Island No. 10, and he spent the next three months as a prisoner of war. He was exchanged later that summer, and he returned to duty. He surrendered on May 6, 1865, as part of Confederate General Richard Taylor’s command. He received a parole four days later.
He returned to his parents’ household in Baltimore after the war, and he earned a living as a lawyer. He died in Baltimore on April 25, 1915.