James H. Jenkins was born on January 8, 1831, in Morgan County, Illinois, to James Jenkins and Tabitha Bristow. His father was a farmer. The family moved to Texas in 1842, and Jenkins worked as a farmer until the 1850s. He earned admission to the bar in 1858, and he reportedly became an “able and successful” lawyer in Collin County, Texas.
He enlisted in the Confederate army on October 9, 1861, and he mustered in as a sergeant in Company I of the 9th Texas Infantry on November 26. Union forces captured him at Shiloh on April 7, 1862, and he remained as a prisoner of war until October 7, 1862. He rejoined the regiment that fall, and he was promoted to 2nd lieutenant on November 11, 1862. He was captured again on September 15, 1864, during the Atlanta campaign.
He returned to Collin County after the war, and he married Margaret Johnson on April 26, 1866. They had at least two children: Oliver, born around 1867; and E.C., born around 1873. By 1870, he owned $4,600 of real estate and $1,800 of personal property. He supported the Democratic Party. He died of cerebritis in McKinney, Texas, on August 31, 1905.