Ordained to the diaconate in April 1950 and priesthood on in October 1950, Hillestad served as an assistant at Christ Church in
La Crosse, Wisconsin from 1950 to 1951, then at the Church of the Ascension in Chicago from 1951 to 1957. He then returned to Wisconsin to serve as vicar of St. Mark's church in
Oconto, Wisconsin (1957–64) before moving to the
Episcopal Diocese of Springfield, where he accepted a call to serve at St. Andrew's Church in
Carbondale, Illinois (1964–1972). Hillestad was selected as the diocese's bishop coadjutor, and Presiding bishop
John E. Hines led the consecration on February 19, 1972, joined by Springfield's bishop
Albert A. Chambers (who would shortly leave the
Anglican Communion due to his opposition to the ordination of woman as priests) and bishop
Frederick B. Wolf of
Maine. Bishop Hillestad took office as the diocese's eighth bishop on September 24, 1972. Rt.Rev. Hillestad submitted his resignation from his see in 1980, citing health reasons. The diocese selected
Donald M. Hultstrand as his successor. In retirement Hillestad served at the Easter Seals Rehabilitation Center in
Mobile, Alabama, before moving in 1989 to
San Miguel de Allende,
Mexico, where he continued to volunteer his time serving handicapped children at the Centro de Crecimiento. ==Death==