James M. Robb was born around 1837 in Ohio. He enlisted in the Union army on August 19, 1861, and he mustered in as a private in Company G of the 27th Ohio Infantry later that day. The regiment took part in the siege of Corinth. He mustered out on June 19, 1863, and enlisted in the Mississippi Marine Brigade.
Robb returned to Ohio after the war, and he married a woman named Margaret. They had at least two children: Bertha, born around 1871; and George, born around 1873. They lived in Deerfield, Ohio, and Robb worked as a farmer. By 1870, he owned $500 of personal property. They moved to Kansas in the early 1870s, but they probably settled in Hamilton County, Ohio, in the mid-1870s. Robb died in Hamilton County on March 29, 1875.