Civil War Union Brigadier General. Born in Ridgeville, Warren County, Ohio, he graduated from Augusta College in Kentucky in 1834 and earned a law degree from Harvard Law School in 1838. He was admitted to the bar and practiced as an attorney in Cincinnati, Ohio. When the Civil War began, he helped to organize the 75th Ohio Volunteer Infantry with Colonel Robert Riley for service in the Union Army and was commissioned as Colonel on September 18, 1861. He led the regiment during operations in western Virginia and commanded a brigade at the Battle of Cross Keys on June 8, 1862. He participated in the 2nd Battle of Bull Run and was promoted to Brigadier General on November 29, 1862. With the Army of the Potomac, he commanded the 2nd Brigade in the 1st Division of the XI Corps during the Battle of Chancellorsville. McLean fell into disfavor with Corps Commander, General Oliver O. Howard, because of his inability to organize his troops after Stonewall Jackson's flank attack during the battle and was relieved of his command. He was transferred to the Ohio Valley and became Provost Marshal of the Department of Ohio. The following year, he was placed in command of a brigade in the 1st Division of the XXIII Corps during the Atlanta Campaign. After the Battle of New Hope Church, he faced disapproval from General Howard again and was relieved of his command for a second time. McLean was transferred to serve under Major General Sherman during the Carolinas campaign to command the 3rd Brigade in the 2nd Division of the XXIII Corps. He resigned on April 20, 1865, returned to Cincinnati, and resumed his law profession. He later retired from public life, moved to Minnesota, and became a farmer. He died at Bellport on Long Island in New York in 1905 when he was 89 years old. He was the son of John McLean, U.S. Supreme Court Associate Justice, and the nephew of William McLean, U.S. Congressman. Two of his nephews were officers for the Confederate Army.