Thank you for the information and pointing me in the right direction. In my haste, I didn't try all the various spellings of WIGEN in the Censuses. Also, did not look beyond cemetery index at UW-Stout ARC online. Admittedly, sloppy research on my part.
Appears that Ellen WIGEN (WIGAN, etc.) of Dunn County is the daughter of Christen HANSEN and Sidsel ERIKSDATTER, of Hagen farm in Fåvang in Ringebu. Born Eli (or Elen) 11 Jun 1843, according to Ringebu Parish records. She is listed as 'Ellen' WIGAN, as you noted, in 1900 Census, widowed and living with sons Martin and Gust, and daughter Anna.
Halvor was born 15 Mar 1838 at Vigen in Yttre Rendal in Hedmark. His father was Gjelvald (or Gjetvold) SIMONSEN. The 1865 Census of Rendal, at Norwegian Digital Archives, lists the family name as "Gjetvoldsen". I don't know which is correct.
Halvor and Eli's oldest son was Simen (Simon), born 26 Aug 1865 at Hagen.
Would like to know when Halvor and Ellen died and where they are buried.