Bishop Kortenhof entered the seminary for the Archdiocese of Chicago of the Roman Catholic Church where he attended for a number of years. Bishop Kortenhof left the Roman Catholic seminary and shortly began his training under the guidance of Archbishop Robert Lane while in Chicago. Bishop Kortenhof was ordained to the Holy Priesthood by Archbishop Lane on September 10, 1978. Upon ordination he served many years as an Associate Pastor working closely with Archbishop Lane and the other Associate Pastors at the Church's parish; Saint Mary Magdalene, located in the 900 Block of West Belmont Avenue in Chicago, Illinois.

 Bishop Kortenhof received a mandate from Archbishop Lane to the episcopate and was consecrated by Archbishop Lane assisted by Bishop Karl Barwin of the Evangelical Catholic Church and Bishop Richard Kuolt, also of the Old Roman Catholic Church, English Rite on May 25, 1991, as Bishop Coadjutor with right of succession.