Mitchell was born on the 2nd of July, 1925, in Hatfield, Wisconsin, to Mitchell and Lillian and was the oldest of their children. The family was of the Ho-Chunk Native American tribe and Mitchell went to school at the Nellsville High School in Black River Falls, where primarily Native American students attended. He dropped out of high school at the age of sixteen and enlisted in the US Marine Corps with the permission of his father, on the 11thof August, 1941.

Mitchell was assigned to the 2nd Battalion, 9th Marines at Camp Elliot in California, and he volunteered for the 2nd Marine Raider Battalion, known as Carlson's Raiders. He was assigned to the Weapons Platoon of F Company and was deployed with the Raiders to Guadalcanal on the 4th of November, 1942. During The Long Patrol, a 28 day jungle patrol to silence the Japanese artillery on Henderson Field, Mitchell was plagued with several rounds of tropical diseases, as well as lost 75 pounds, and was sent off the island for medical treatment on the 4thof December.

Mitchell was offered medical discharge due to the diseases he had contracted but he refused and requested to be sent back to a combat unit. Once healed, he was attached to the Weapons Platoon, Company A, 29th Marine Regiment, 6th Marine Division, and was deployed to Okinawa for the invasion on the 1st of April, 1945. A month into fighting, Mitchell was shot through the shoulder and evacuated to Guam for recovery before being honorably discharged as a Sergeant following the end of the war. He decided to reenlist in 1948 but this time with the US Army. He wasn't allowed to retain his rank from the Marine Corps and was assigned to Company E, 2nd Battalion, 19th Infantry Regiment, 24th Infantry Division. This division was the closest unit to the Korean Peninsula when war began on the 25th of June, 1950, and Company E was one of the first units to enter the country and it was Mitchell's actions on the 5th of November, 1950, that would cost him his life and earn him the Medal of Honor. The citation reads:

Cpl. Red Cloud, Company E, distinguished himself by conspicuous gallantry and intrepidity above and beyond the call of duty in action against the enemy. From his position on the point of a ridge immediately in front of the company command post he was the first to detect the approach of the Chinese Communist forces and give the alarm as the enemy charged from a brush-covered area less than 100 feet from him. Springing up, he delivered devastating pointblank automatic rifle fire into the advancing enemy. His accurate and intense fire checked this assault and gained time for the company to consolidate its defense. With utter fearlessness he maintained his firing position until severely wounded by enemy fire. Refusing assistance he pulled himself to his feet and, wrapping his arm around a tree, continued his deadly fire again, until he was fatally wounded. This heroic act stopped the enemy from overrunning his company's position and gained time for reorganization and evacuation of the wounded. Cpl. Red Cloud's dauntless courage and gallant self-sacrifice reflects the highest credit upon himself and upholds the esteemed traditions of the U.S. Army.

Mitchell's mother received his Medal of Honor from General of the Army Omar Bradley in a ceremony at the Pentagon on the 25th of April, 1951. Camp Red Cloud in South Korea, Red Cloud Range in Fort Benning, Georgia, the Red Cloud Memorial Park in Komensky, Wisconsin, and the USS Red Cloud, a Watson-class vehicle cargo ship that was christened by his daughter Annita in 1999, all bear his name. Mitchell Red Cloud Jr was originally buried at a UN Cemetery in Korea but was exhumed and moved to Wisconsin in 1955 where he was buried off the Winnebago Mission in the Decorah Cemetery in Black River Falls, Wisconsin.