Besides the Onthank family of whos decendants trace thier linage to Christopher Unthank/Onthank, there are two other family groups in the Unitied States whose roots are undoubtedly in the English Unthank Family. In one case the name is unchanged from that of its earliest forebears, "Unthank"; in the other case the transition to "Onthank" has again been made.
So far as is known, and assiduous research on the subject has been made and continues, neither of these branches of the Unthank Family of Britian has any immediate relationship to Christopher Unthank/Onthank, the first immigrant with that surname, in 1634-35.
I. The American Unthank Family
According to the manuscript of "Record and History of the 'Unthank Family' in America," compiled in 1932 by G. R. Unthank, of Lincoln, Nebraska, the first immigrant to America of his family group was Joseph Unthank, who was born in Yorkshire, England, date undetermined. Joseph and his wife, Ann, who were Quakers, came to Philadelphia, Pennsylvania, in or about 1740, and a few years later mave to Springfielf, in Bucks County of that State. A son, John, was born to them at Springfield in April, 1741. In 1755, Joseph and his family moved to Guilford County, North Carolina.
The North Carolina Unthank family, as was true of most early Eastern families, soon spread to the west, and are found in the early 19th century in Tennessee and especial Indiana.
There can be found a "A. H. UNTHANK, 1850" carved into Register Cliff near Glenrock, Wyoming. This marking was done by Alvah H. Unthank, who's marked grave is found half-mile to the east of the Cliff. He died of "camp-fever" on July 2, 1850 while traveling with a group to California.
Further Unthanks spread to Ohio, Michigan, Nebraska, California and Washington.
II. The Onthank Family from Ireland
The Origin of the Unthank or Onthank Family in Ireland is obscure. the only reliable explanation thus far has come from Herbert William Unthank, of Exeter, England with whom the Arthur Heath Onthank, writer of The Onthank Family book, met with for a day in May 1956. Mr. Unthank, a University Lecturer at the University of Exeter, came from the Unthank family in Ireland, and has his family genealogy amoung the Irish Unthanks accurately recorded for seven generations past. He belived that the earliest Unthank there was one of the soldiers of Oliver Cromwell, who conquered Ireland in 1650, and subsequently settled many of his soldiers, and others from England, on land in Ireland in order to maintain the pacification. Herbert William Unthank's forebears were Quakers and they settled in and near Limerick, Ireland.
A branch of these Onthank's from Ballyfin Queens County, Ireland immigranted to in or around the Baltimore, Maryland area around 1850 until 1890. They then moved to Cheyenne, Wyoming and Later Pocatello, Idaho. Further spread includes Butte, Montana, Spokane Washington, Portland Oregon along with possibly California.
From "The Onthank Family: Its History and Genealogy" A. H. Onthank, 1959