Perhaps they came from an area that other early settlers were from?
"Translated from 'Nordmændene i Amerika' by Martin Ulvestad. 1907.
Nels Mickelsen† from the Røraas area was the first Norwegian in Douglas County. He settled in the vicinity of Holmes City in 1865. At that time there were Indians in the neighbourhood. In 1866 many Norwegians came, of whom can be named; John Arntsen from Kobbervik, Ole Brandson† from Hedemarken, Ole Urness†, Lars Grinden† and Amos Johnson†, all from Sogn, Mathias Wolstad†, Sivert Olsen† and Hans Pedersen, all from Hedemarken, Gunder Johnson and Ole Hammer from Trondhjem, Renhard Bottner† from Solør. Petter E. Julin from Hammerfest, Ole Ellefsen from Telemarken as well as Petter Stenstrup, Tore Evensen†, Ole Amundsen†, Albert Barsness, Torsten Hovde, Gunder Knudsen, Jens Gundersen†, Charley Brown†, Karm Øen, Ole Pedersen and Johannes Olesen."...
translated by Olaf Kringhaug
But there was a great reduction in number of Norwegian immigrants during the US civil war, it would have fairly unusual to have come over in 1861.
There also appear to be Norwegian families in Douglas county who used name Eidem which struck me as very similar to Adams.
You have a tough one.