Charles James Guth was born September 21, 1923 in Passiac, New Jersey to Conrad and Ethel Chapman Guth. His father was a farmer. His family was nominally Christian, but he did not have a personal conversion experience until his late teens. He graduated from the Bridgeton, New Jersey High School in June 1941 and then went to the Philadelphia School of the Bible. During this time he also worked in the Cumberland National Bank of Bridgeton, first as bookkeeper and then as a teller. After graduating from PCB in June 1944, he went on to Wheaton College and graduated from there with a bachelor's degree in June 1947. He worked his way through college to pay part of his tuition. That summer he attended the Summer School of Linguistics at the University of Oklahoma and while there met his future wife, Betty Jean Bear.

At about this time he applied and was accepted as a missionary by Sudan Interior Mission. In 1948, after a short period of orientation and training, he left for on a freighter for the Sudan, then in essence a British colony. After landing at Port Sudan and spending a few weeks in Khartoum, where he began his language study of Arabic, he and fellow missionary Sam Burns were assigned the task of starting a mission station among the Koma people in southern Sudan, near the Ethiopian border. They decided on a site at Yabu's Bridge, which was the base of their activities for during his work with the Komas. Guth and Bur ns engaged in evangelistic work and also often gave tribespeople simple medical assistance. In 1949, he and Betty, who had also come to Africa as a SIM missionary, were married. Shortly afterwards, they returned home on furlough.

Sometime after they returned to the Sudan, the Guths were transferred to Doro, where Charles was head of the mission station in the territory of the Mobassan people. The station included a church, boy's school, and hospital. Later Guth developed plans for a Bible school there as well. The Guth's four children, Carol (1950), Judi (1951), Charles (1955) and Douglas (1957), were born in Africa. The family returned to the United States around 1958 and went back to the Sudan in December of the same year.

In 1962 the Guths had to return to the United States because of Betty's health problems. Charles attended graduate school at the State University of Iowa from 1962 to 1963 and received graduate credit in art and journalism. In August, 1963 he was appointed to literature ministry at the SIM headquarters in Toronto, where he did artwork, layout and assisted in the production of the missions magazine and other publications. He continued to serve here through the rest of his missionary career.