Duncan Ronald McAllister was born around 1830 in Scotland to Ronald and Elizabeth McAllister. His father was a farmer who owned $800 of real estate by 1850. The family immigrated to America by the 1840s and settled in Preston, Connecticut. By 1850, McAllister was working as a mariner.
He married a woman named Betsey in the 1850s, and they had at least two children: Henrietta, born around 1858; and Elizabeth, born around 1862. By the early 1860s, they were living in Chicopee, Massachusetts.
McAllister enlisted in the Union army on May 31, 1861, and he mustered in as a private in the 10th Massachusetts Infantry. According to his service records, he was 5 feet, 5½ inches tall, with black hair and blue eyes. He was detailed for surveying duty in the spring of 1862. He was reportedly “frequently drunk” while on duty, and Union officers sent him back to his regiment later that year. In March 1863, he was absent without leave for at least three days. He faced a court martial and received a fine of $13. He remained fiercely loyal to the Union. Had the Union army triumphed at Chancellorsville, he insisted in May 1863, “this ware wold be about a[t] end and the army of the Potomick wold have ben in Richmond and the hart of this Rebelion crushed finer then pouder.” He mustered out on July 1, 1864.
He returned to Chicopee after the war, and he probably died in the late 1860s.