McComas was born in Cincinnati. He began his career as a Special Artist with drawings of scenes of the Northern Virginia campaign published in New York Illustrated News on June 29 and July 13, 1861. The first drawing, of the twenty-one by McComas Frank Leslie’s Illustrated News would eventually publish, appeared on September 21, 1861. It was of Paducah, Kentucky where he was assigned as Special Artist to Brigadier General Ulysses S. Grant’s army, which he accompanied to Bowling Green, Kentucky and the Battle of Pittsburg Landing, Tennessee before enlisting as a 2nd Lieutenant in the 79th Ohio Infantry in 1862. He continued to send drawings to New York throughout his military career. In 1863, he was detailed as a topographical engineer first to Major General John McClernand’s staff and later to various other generals for the duration of the war. General McClernand cited McComas for commendation in his report of the Battle of Champion’s Hill, Mississippi in May 1863. McComas was promoted to Captain in August 1863 and continued to serve in campaigns in Texas until he was discharged in 1865, and he returned to Cincinnati. The Becker Collection contains two drawings by McComas.