On August 10, 1889, William Henry Kielhorn was born in Evansville, Indiana. In 1914 he married Glenna Monroe, and together they had two children. Kielhorn studied at the Moody Bible Institute in Chicago and earned a certificate in 1925. He was ordained by the Presbytery of Southeastern Illinois of the Presbyterian Church in the USA on May 12, 1927. He served a PCUSA congregation in Golconda, Illinois for four years before taking a dual call to the Douglas PCUSA in Endeavor, Wisconsin and the Oxford PCUSA in Oxford, Wisconsin. As modernism increasingly exerted control of the Winnebago Presbytery of the PCUSA, Kielhorn found friendship and fellowship with other conservatives, such as Arthur Perkins, Harold Hillegas, and John DeWaard. Kielhorn was one of the original directors of the Crescent Lake Bible Camp near Rhinelander, Wisconsin. Kielhorn was among the fourteen men charged by Winnebago Presbytery over their involvement in the Crescent Lake Camp, though only Arthur Perkins was brought to trial on those charges. Kielhorn attended the first General Assembly of the OPC in June 1936. He signed the card, subscribed with the other ministers and elders, voted and took part in the Assembly. Due to a clerical error, his name was omitted from the list of ministers and elders that was published in the Presbyterian Guardian. Kielhorn considered himself a member of the new denomination, and after extended correspondence, the oversight was corrected and he was included among the constituting members of the denomination. Kielhorn also attended the first meeting of the new Presbytery of Wisconsin and Upper Michigan, held in Merrill, Wisconsin on July 30, 1936. When the moderator of the new Presbytery, the Rev. Arthur Perkins, was unable to serve due to a nervous breakdown, Kielhorn took over as moderator. He served as the moderator until September 24, 1937, when he asked that his name be erased from the roll of the Presbytery.
Kielhorn served as the pastor of the Community Bible Church in Oxford, Wisconsin until 1942. Because he had never formally renounced the jurisdiction of the Presbyterian Church in the USA, he was harassed by his old Presbytery for several years following his departure. A civil suit related to church property in Douglas, Wisconsin, was brought against him by the PCUSA. Eventually Kielhorn was received by the Independent Fundamental Churches of America. He passed on to glory in 1947.