Thorsness was born February 14, 1932, in Walnut Grove, Minnesota, where his family had a farm. There, he earned the Eagle Scout award from the Boy Scouts of America. He is one of only nine known Eagle Scouts who also received the Medal of Honor. The others are Aquilla J. Dyess and Mitchell Paige of the U.S. Marine Corps, Robert Edward Femoyer and Jay Zeamer Jr. of the U.S. Army Air Forces, Arlo L. Olson, Benjamin L. Salomon of the United States Army, and Eugene B. Fluckey and Thomas R. Norris of the United States Navy. In 2010, Thorsness received the Distinguished Eagle Scout Award.