Nels Schmidt Rattenborg was the son of Willads S. Rattenborg and his wife Bodvil Vind, the widow of Nels Christensen. Nels had a one half-blood sister, Sinit Christensen, a brother Hans Rattenborg (b.1873), and a sister Helena "Lena" Rattenborg (b. 1876, married Lauridsen). While in school, Nels and Hans changed their name from Rottenborg to Rattenborg, due to being teased about being "rotten".

Nels' mother Bodvil Vind died 3 August 1877, age 29 years, in Denmark. Nels' father Willads then married Marie Hansen (b.1 Jan 1860) in 1878. Willads S. and Marie immigrated to America with Willad's three children, and settled on a farm known as "Ingerslev" in Audubon County (no buildings are there in 2014).

Nels' had 7 half-blood siblings, children of Willads S. & Marie: 1. Andrew (b. 1880, d.24 Dec 1941); 2. Christina Rattenborg Olsen (b.1882, d.1946); 3. Ingeborg Rattenborg Olsen Sorensen (b.1882); 4. Willis Rattenborg (b.1885); 5. Marie Rattenborg Christensen Petersen (b.28 Apr 1887, d.18 Sept 1981); 6. Peter Rattenborg (b.23 Dec 1890); 7. John Rattenborg (b. 28 Oct 1900).

Nels grew up on the old ridge road farm in Section 23, Sharon Township, Audubon County, IA, in a home which they built and painted. This was the first painted home in the Elk Horn area, quite an item of interest.

In 1892, Willads Schmidt Rattenborg returned to Denmark and brought back two young girls, Anna Katrine Holm and Marie. (Marie later married Carl Beck in Audubon). Anna Katrine stayed with (her mother's sister) Aunt Marie and Uncle Lawrence Nissen, also living on the old ridge road, Sec. 23.

On 28 February 1893, Anna Katrine Holm married Niels Schmidt Rattenborg in the parlor of his parents' home. (To this union, a total of 11 children were born). Niels and Ann moved to a farm 2 miles south & 2 miles west of Hamlin, IA. There 3 daughters and 1 son were born. Christina Rattenborg Hansen (b.9 Aug 1894, d.20 May 1955); Soren Rattenborg (b.16 May 1896, d. 26 July 1964); Anna Rattenborg Bertlesen Hansen (b.16 June 1898, d.11 Feb 1982); Marie Rattenborg Gude Lonigan (b.28 May 1900).

About 1902, Niels and Anna bought land north of Hwy 71, in old Hamlin, IA. They laid out 5 lots north of the highway on Main Street, and sold those lots. On the farm north of the Hamlin school, two more children were born: Agnes Rattenborg Christensen Coats (b. 17 Mar 1902); Ella Helena Rattenborg Rasmussen (b. 8 Oct 1904).

Neils and Anna sold this farm and built a new farm on the hill east of present town of Hamlin. More children were born at this location: Willads S. (b. 10 Jan 1907, d.25 Sept 1975); Otto Rattenborg (b. 21 Sept 1908, d. 1 Feb 1978); Freda Rattenborg Alwill (b. 4 May 1911); Emma Rattenborg Hansen (b. 18 Apr 1913); and Herbert Rattenborg (b. 9 Apr 1915).

Niels and Anna Katrine were members and leaders of the Hamlin Lutheran Church. Danish language was spoken in the church from 1904-1918. Niels was a charter member of Farm Bureau.

In 1922, Anna Katrine and Niels rented their land out and went to Standard, Alberta, Canada where Willads S. Rattenborg (Niels' father, deceased) had 160 acres. The younger children attended school there. After the threshing season in Oct. 1922, the family returned to Hamlin.

On 11 June 1949, Niels died of a blood clot in his home. Anna Katrine died in 1951 at St Anthony's Hospital, Carroll, IA. Both are buried in the Hamlin Cemetery which was part of their 200 acre farm.