I recieved this from a friend. I expanded on it slightly
How many US Presidents do you know of were general officers in the Civil War?
Ulysses S. Grant, 18th President
At the outbreak of the Civil War he was appointed by the Governor of Illinois to command an unruly volunteer regiment. Grant whipped it into shape and by September 1861 he had risen to the rank of brigadier general of volunteers. He sought to win control of the Mississippi Valley. In February 1862 he took Fort Henry and attacked Fort Donelson. President Lincoln promoted Grant to major general of volunteers. Grant maneuvered and fought skillfully to win Vicksburg, the key city on the Mississippi, and thus cut the Confederacy in two. Lincoln appointed him General-in-Chief in March 1864. Grant directed Sherman to drive through the South while he himself, with the Army of the Potomac, pinned down Gen. Robert E. Lee's Army of Northern Virginia. Finally, on April 9, 1865, at Appomattox Court House, Lee surrendered
Rutherford B. Hayes, 19th President.
He fought in the Civil War, was wounded in action, and rose to the rank of brevet major general. While he was still in the Army, Cincinnati Republicans ran him for the House of Representatives. He accepted the nomination, but would not campaign, explaining, "an officer fit for duty who at this crisis would abandon his post to electioneer... ought to be scalped."
James A. Garfield, 20th President
In 1862, when Union military victories had been few, he successfully led a brigade at Middle Creek, Kentucky, against Confederate troops. At 31, Garfield became a brigadier general, two years later a major general of volunteers. Meanwhile, in 1862, Ohioans elected him to Congress. President Lincoln persuaded him to resign his commission: It was easier to find major generals than to obtain effective Republicans for Congress. Garfield repeatedly won re-election for 18 years, and became the leading Republican in the House.
Benjamin Harrison, 23rd President
Harrison was a brigadier general fighting in the Atlanta campaign
William McKinley, 25th President
McKinley, while serving honorably did not achieve the rank of General. However he was a major during the civil war in the guard. Enlisting as a private in the Union Army, he was mustered out at the end of the war as a brevet major of volunteers.