Civil War Union Brevet Brigadier General. Born in Wilmington, Clinton County, Ohio, he studied medicine, and graduated from Jefferson Medical College in Philadelphia, Pennsylvania in 1850. He established a medical practice in Adams County, Ohio, and in 1861 was elected as a Democrat to the Ohio State Senate. While in the state legislature, he supported the suppression of the Southern secession and opposed many in his party for the anti-war policies. After attending legislature sessions in early 1862, he volunteered his services to the Union Army, and was commissioned as Lieutenant Colonel of the 91st Ohio Volunteer Infantry on August 10, 1862. Mustered into Federal service on September 7, 1862 with his regiment, he then accompanied his men as they traveled under the command of Colonel John Alexander Turley to what became West Virginia, where it was assigned to the VIII Army Corps. Over the two years the regiment operated largely in operations and raids against Confederate forces in that theatre, with the exception of the pursuit of Confederate cavalry raider General John Hunt Morgan though Indiana and Ohio. Benjamin F. Coates participated in the May 9, 1864 Battle of Cloyd’s Mountain, West Virginia, and in May and June 1864 he was with the regiment participated into raids lower Virginia under Major General David Hunter. In a skirmish at Lynchburg, Virginia Colonel Turley was shot in the leg, and his wound forced him to eventually resign his commission and return home. Lieutenant Colonel Coates assumed command of the regiment, and led it until September 19, 1864, when he was elevated to command the 2nd Brigade of the 2nd Division of the Department of West Virginia. He led the brigade through the balance of Major General Philip Sheridan’s Shenandoah Valley Campaign, and commanded it at the October 19, 1864 Battle of Cedar Creek. He was promoted to full Colonel on December 9, 1864, and was returned to command the 91st Ohio Infantry in April 1865. He was brevetted Brigadier General, US Volunteers on March 13, 1865 for "efficient and meritorious services". He was honorably mustered out on June 24, 1865. He had been wounded once during his service (August 1864 at Halltown, Virginia) and would occasionally be given leaves of absences by Army command so he could sit in session in the Ohio legislature, having switched to the Republican Party. He relocated to Portsmouth, Ohio in July 1865, and went on to serve in a number of local and county positions, including collector of internal revenue for fifteen years. In his later years he served as a receiver for a railroad company. He passed away in Portsmouth in May 1899.