Hi Dan, I'd be glad to try to help, but not sure you're still out there. You've got two responses and haven't checked in with them. I'll post a bit here and then wait for your response! Thanks.
On an Ancestry.com message board you wrote:
I need help finding where my family arrived in America and what ship they may have been on. Christian Jensen Aalborg (born 1833) arrived in the U.S. around 1865 with his wife Sophia Marie and two sons Abraham and Charles. Their third son, Aaron, was born in Racine, Wisconsin about 1870. I learned this from Aaron's obituary.
It also said they stayed in Wisconsin until about 1875 when they left for Turner County, South Dakota. I have been unable to find any records of them in Wisconsin or anywhere else besides South Dakota.
I found a passport record for their son Nathan. It says that his father, Christian, was born in Denmark and that he emigrated to the U.S. from the port of Aalborg about 1866. This is about all I've been able to find on their arrival.
I'm having trouble logging in there so will respond here. Looks like you need their Danish roots?
Okay, I think Sophie Marie was born about 1843 in Hjørring amt as Sophie Marie Jensen, daughter of Jens Holgersen.
Below, I've posted the 1840, 1845, and 1850 census.
Some definitions of words in the census:
gift = married; ugift = unmarried
husmand lever af sin jordlod = a smallholder farmer living on his plot
hans kone = his wife; deres barn / deres børn= their child; enke = widow
daglejer, deres svigersøn = day laborer, their son-in-law
aftaegtskone = a pensioner provided for here
Last entry for each person is their birthplace
1840 CENSUS - Sophie Holgersen isn't born yet.
Hjørring, Dronninglund, Hellevad, Pelleborg, Hus, 75, , FT-1840, B5847
Palle Hansen 65 Gift Husmand
Karen Pedersdatter 59 Gift Hans kone
Jens Holgersen 27 Gift Daglejer deres svigersøn
Karen Marie Pallesdatter 25 Gift Hans kone[Palle is an alternate spelling for Poul]
Ansine Krisitna Nielsdatter 2 Ugift Deres barn [this child must have died before 1845]
Aalborg, Kær, Horsens, Vodskov distr. Vesterhinnerup, et hus, 108, FT-1845, A0350
Jens Holgersen 29 gift Husmand lever af sin jordlod. Sindal sogn, Hjørring amt.
Karen Marie Poulsdatter 30 gift hans kone. Ugilt sogn, Hjørring amt.
Caroline Jensdatter 5 ugift deres barn. Hellevad sogn, Hjørring amt.
Sophie Jensdatter 2 ugift deres barn. Hellevad sogn, Hjørring amt[born about 1843]<-----------------------
Martine Iversdatter 59 enke Aftægtskone. Sulsted sogn, Aalborg amt
Hjørring, Hvetbo, Jetsmark, Lundbakshede, et Huus, 117, FT-1850, D2547
Jens Holgersen 35 Gift Huuseier, Huusfader, lever af sin Jordlod Sindal Sogn, Hjørring Amt
Karen Marie Pallesdatter 36 Gift born in Ugilt Sogn, Hjør amt
Caroline Sophie Jensen 9 Ugift deres Børn born in Hellevad Sogn, Hjør amt
Sophie Marie Jensen 7 Ugift deres Børn born in Hellevad Sogn, Hjør amt <----------------------
You also wrote: "I think that Jensen was their original surname. I believe they took the surname Aalborg when they arrived in South Dakota. They did this I think because there was another Christian Jensen living in the same town when they came to South Dakota. I can't prove this yet, but, I've been told by family that Aalborg was not the original name. Hope someone can help."
You can read about Danish naming practices here:
It was typical for a Dane to have a first name, maybe a middle name, then a patronymic name, then an "identifier" name.
The patronymic name is like our surname.
The "identifier" name is also like our surname.
In other words, when Danes dropped their old naming system and chose permanent surnames, some kept their patronymic name, and some kept their "identifier" name. Christian Jensen Aalborg is of the era when Danes who got to choose their own surname.
The patronymic name is the father's first name plus "son" or "daughter." So a dad named Jens would have children baned Jensen and Jensdatter. Your Christian had a dad named Jens. In the mid-1800s "datter" got dropped and both girls and boys used "sen."
Probably. Your head will swim if I say the exceptions. It has to do with the fact that Danes adopted the new surname system over about a century. Like they say on facebook, "it's complicated."
The identifier name is an occupation, place of origin, or place of residence. When I see the name Aalborg, I'm thinking this family, at some point in their history, lived in Aalborg, Denmark. A very Danish name.
In records in Denmark, Christian and others might be found sometimes with both "last" names, sometimes with just one. So if you have family members who know Christian was called "Christian Jensen" in Denmark, great, I can believe that. But it doesn't mean he wasn't also Aalborg. Like John F. Kennedy can also be called Jack Kennedy - both names can be recognized as the same person.
Christian Jensen is a sadly common name and so far I haven't found him. I haven't found him under the name Aalborg. However, I've looked only in the amts where his wife had lived. His immigration record would help - but you said you didn't find it on Ancestry.com? I didn't find it at Dansk Demografik Database www.ddd.dda.dk.
And yes indeed, when Danes got to choose a permanent surname, many did use their "identifier" name instead of their patronymic name for exactly the reason you say: too many people with the same name Jensen, Andersen, Hansen, Sorensen! Aalborg - that's more rare.