Looking for Knudt Johnson's birth record

I found the name of a new relative the other day and am quite excited. I could use your help locating his birth, or emigration record. Here' s what the text that led me to him

quote:The Johnson brothers, Halvor and Knut (Fie). These brothers came to America from Nissedal, Telemarken, in 1852. The older brother, Halvor, was a sailor and engaged in the sailing business on the lakes here for about three years. He then bought land in this town and developed a farm of goodly proportions, and lived on it until his death. He is survived by two daughters, Anna and Thea, and one son, John, who has been in the mercantile business for many years in the village of Hollandale. ... His brother Knud did not live very many years in the town. He enlisted in the Civil War in 1861, joining the Dodgeville, Wis., Guards, which in due time was joined to the Twelfth Regiment Wis. Volunteers. After being honorably discharged he moved to Lake Mills, Iowa, where he has since resided up to this date. He has been elected to various town and county offices during his life. He is now a retired farmer living in the village of Lake Mills.

I very sure that the Halvor is the brother of my 3rd great grandmother. But I was unaware of a brother Knut/Knudt. but based on the above, found he was born 1841 and died around 1921. From that I was lead to

quote: KNUDT JOHNSON Many of the most highly honored citizens of Lake Mills are retired farmers and among this number is Knudt Johnson. He is a native of Norway but has resided in this country since boyhood and no native born American has given more undivided loyalty to the United States than he. At the time of the Civil war he bore arms in defense of the Union and in times of peace he has always subordinated private interests to the general welfare. His birth occurred in Norway, September 12, 1841, and his parents were John and Ingeborg (Hanson) Torgeson, the latter of whom died when her son Knudt, the youngest of eight children, was but five years old. In 1853 the father with his son Knudt and another child came to the United States and located near Madison, Dane county, Wisconsin, where an older brother had taken up a homestead in 1849. The father died upon that place in 1876 and is there buried. Source: History of Winnebago County and Hancock County, Iowa

The parents were John Torgerson and Ingeborg Ansteensdatter (her father Ansteen Hansen). The family migrated to Flogstad Annex, Dypvåg, Aust-Agder, Norway Nov 9, 1839 Migration Record #12 Ingeborg died Jun 18, 1847 I would very much appreciate any help locating Knudt's birth, confirmation or his emigration record. I believe John's was dated 1851.