Eli Long was born in Woodford County, Kentucky, on June 16, 1837. He attended the Frankfort military school, was graduated in 1855, and the following year was appointed, directly from civilian life, a second lieutenant of the 1st U. S. Cavalry. After service on the frontier he became a first lieutenant on March 1, 1861, and captain on May 24 in the promotions incident to the withdrawals of those officers who had elected to "go South." He transferred to the 4th Cavalry in August in order to secure active duty, and at the battle of Murfreesboro was wounded in the arm while commanding Company K. Soon after he was appointed colonel of the 4th Ohio Cavalry, a regiment of volunteers whose morale had suffered greatly a few days before by being compelled to surrender to the Confederate raider, John Hunt Morgan. Long revitalized the command and led it in the Tullahoma and Chickamauga campaigns; he directed a brigade in the latter. During the Atlanta campaign in June, 1864, his brigade joined the Cavalry Corps of the Army of the Cumberland, and Long was promoted brigadier general of volunteers on August 18, 1864. At the end of October he was sent to Nashville to take charge of Kenner Garrard's division, which he was to collect, equip, and remount, pending future operations. These were not long in coming; they included the Confederate General J. B. Hood's thrust into Tennessee and culminated in the decisive battle of Nashville in December and General James Harrison Wilson's raid from west to east through what remained of the Confederacy in the spring of 1865. During this period Long commanded the 2nd Division of Wilson's Cavalry Corps, was badly wounded for the fifth time at Selma, and after the fighting was over was assigned to command of the military district of New Jersey. General Long was awarded every brevet in both the regular and volunteer services for gallant and meritorious service up to and including the grade of major general. He was retired from the army with the rank of major general in 1867 (reduced to brigadier in 1875), and subsequently took up residence in Plainfield, New Jersey. Here, according to his obituary in the Plainfield Courier-News of January 8, 1903, he practiced law and was borough recorder. He died in a New York City hospital as the result of an operation on January 5, 1903, and was buried in Hillside Cemetery, Plainfield.
Reference: Generals in Blue. Lives of the Union Commanders by Ezra J. Warner. Louisiana State University Press. Baton Rouge.