Jacob D. Cox was born in Montreal, Canada to American parents on October 27, 1828. A year later, his family moved back to New York City. He was privately educated in his early years, and in his teenage years he worked as both a law office clerk and a bookkeeper in a brokerage firm. He decided to pursue the ministry and graduated from Oberlin College in 1850. While there, he married Helen Clarissa Finney, daughter of the renowned evangelical preacher and college faculty member, Charles Grandison Finney. He and Helen eventually had eight children. After graduation, Cox took a position as superintendent of the school system in Warren, Ohio and continued studying law. He was admitted to the Ohio bar in 1853, and helped organize the Republican Party in the state. He was elected to the Ohio Senate in 1860 and accepted a commission as a brigadier general in the Ohio militia.
Cox's first Civil War duty saw him commanding a recruiting station in Ohio, then taking over command of the Kanawha Brigade. The brigade performed well in the Kanawha Valley Campaign and was transferred to the Department of Virginia in 1862. Eventually, the unit was reorganized as the Kanawha Division, IX Corps, Army of the Potomac. The division fought in the Battle of South Mountain and the Battle of Antietam, as part of the Maryland Campaign of 1862, and Cox was appointed major general in October. However, his appointment was rescinded as part of a reorganization of the army. In 1863, Cox commanded the District of Ohio and, later, the District of Michigan.
By 1864, Cox was put in command of the 3rd Division, XXIII Corps, Army of the Ohio, under Maj. Gen. John M. Schofield. Cox's command took part in the Atlanta Campaign and the Battles of Franklin and Nashville before being transferred to the North Carolina coast. On December 7, 1864, Cox was again promoted to major general. Cox continued to command his division throughout the Wilmington Campaign before taking command of the District of Beaufort. In March 1865, Cox's force left New Bern, marching west to unite with Gen. William Tecumseh Sherman's forces near Goldsboro. Cox's men fought at the Battle of Wyse Fork, March 8-10, 1865 and continued fighting under Schofield through the remainder of the Carolina Campaign. Cox mustered out of the service at war's end.
From 1866 to 1868, Cox served a term as governor of Ohio. He was appointed Secretary of the Interior in 1869 by Pres. Ulysses S. Grant, but resigned in 1870 due to philosophical and political differences with the president. From 1873 to 1878, Cox was the president of the Toledo and Wabash Railroad. He then served one term in the U.S. Congress from 1877 to 1879, before ending his political career. In 1881, Cox became Dean of the University of Cincinnati Law School, a position he held until 1897. Also, within that time, he held the university presidency from 1885 to 1889. He declined an offer from Pres. William McKinley to serve as U.S. Ambassador to Spain in the late 1890s. Cox died on August 4, 1900 while on vacation in Massachusetts.