George B. Miles was born on February 3, 1836, in Chester County, Pennsylvania, to Nathaniel and Sarah Miles. His father was a farmer who owned $300 of personal property by 1860. He lived in West Vincent, Pennsylvania, until the 1850s, when he and his father moved to Salem, Illinois. By 1860, he was working as a miller.
He enlisted in the Union army, and he mustered in as a private in Company K of the 15th Illinois Infantry on May 24, 1861. According to his service records, he was 5 feet, 6 inches tall, with light hair and light eyes. The regiment took part in the Battle of Fort Donelson and the siege of Vicksburg. He mustered out on May 24, 1864.
He returned to Illinois after leaving the army, and he married Ellen Yontz on November 3, 1864. They had at least six children: Amanda, born around 1867; Martha, born around 1868; Julia, born around 1869; Elfie, born around 1875; June, born around 1877; and Thomas, born around 1880. They moved to Monroe, Iowa, in the late 1860s, and he continued working as a miller. By 1870, he owned $700 of real estate and $150 of personal property. They moved to Council Bluffs, Iowa, in the 1870s, and he died there of paralysis on March 4, 1909.