Robert Cooper was born on October 23, 1843, in Washington County, Ohio, to Elisha and Aerial Cooper. His father was a farmer who owned $1,500 of real estate and $300 of personal property by 1860. Cooper grew up and attended school in Ludlow, Ohio.
He enlisted in the Union army on October 9, 1861, and he mustered in as a private in Company F of the 63rd Ohio Infantry. The regiment took part in the siege of Corinth, the Atlanta campaign, the March to the Sea, and the Carolinas campaign. He was promoted to corporal on January 1, 1864, and he mustered out on July 8, 1865.
He returned to Ohio after the war, and he married Mary Ellen Springer on December 6, 1866. They had at least nine children: Christiana, born around 1868; Mary, born around 1869; Margaret, born around 1871; Emaline, born around 1873; Minnie, born around 1875; Charles, born around 1877; Edward, born around 1879; Flora, born around 1883; and Videssa, born around 1890. They moved to Franklin, Kansas, around 1870 before settling in Neosho, Kansas, around 1872. Cooper earned a living as a farmer. According to one writer, he was a “constant and faithful member” of the local Baptist church. He died of cancer of the stomach in Council Grove, Kansas, on May 21, 1906.