Richard J. Poston was born around 1836. By the early 1860s, he was living in Scales Mound, Illinois, and working as a minister. He enlisted in the Union army on August 7, 1862, and he mustered in as a private in Company E of the 96th Illinois Infantry on September 4. According to his service records, he was 5 feet, 11½ inches tall, with black hair and hazel eyes. The regiment took part in the Battle of Chickamauga, the Battle of Lookout Mountain, the Battle of Missionary Ridge, the Battle of Kennesaw Mountain, and the Battle of Nashville. He mustered out on June 10, 1865.
Poston lived in Springfield, Ohio, after the war, and he resumed his work as a minister. He moved to West Virginia in the 1880s. He supported the Republican Party. He died sometime after 1888.