Nels was born on 29 Mar 1853 on the Moen farm in Målselv, Troms, Norge. He was the fifth child of Anders (son of Ole) and Anne Marie (daughter of Ole) from the Brandskognes farm. Anders was the maternal grandson of Nils (son of Jakob), the man who first cleared the Moen farm in the 1790s, which is now the modern town of Moen.

In 1862 at nine years of age Nels immigrated with his parents, siblings, and extended family to Colfax, WI. His family was the first of two families to settle the township. Nels worked on his father's farm there until 1878 when decided to strike out on his own. He arrived in Norman county later that year with a team of oxen.

He homesteaded a quarter section of land in section 26 of Waukon township where he established a home. He was one of the first settlers of that area and one of the early organizers of the township. By the time of his death he had increased his holdings to 399 acres, having donated an acre for a school of which he was a strong supporter. He also played a role in the organization of several institutions in the area, particularly the Waukon Creamery, the Waukon Mercantile Co., and the St. Petri congregation.

On 12 Feb 1887 Nels married Anne (daughter of Asle), then a recent immigrant to Minnesota from Ål, Buskerud, Norge. Anne and Nels had 11 children:

Anna Mathilda 1887-1916
Ida Amalia 1889-1982
Aldred Nicholai 1890-1958
Oscar Adolph 1892-1983
Ingvald Theodore 1893-1990
Ole Kornelius 1895-1981
Clara Theolene 1896-1987
Selius Bernard 1898-1975
Mabel Sophie 1900-1909
Clarence Melvin 1903-1936
Lillian Ovidia 1907-2000

A final note about his name. In his homeland and in the Norwegian speaking community of Dunn county in Wisconsin, Nels was known in Norwegian fashion as Nels Andersen because he was the son of Anders. In the English speaking circles he was sometimes called Nels Olson, as his father was the son of Ole, so Olson became a family name of sorts for the younger children of Anders. When Nels moved to Minnesota, however, he adopted the name of the farm where he was born and retained the "O" of his father's patronym as a middle initial.