Navigating Danish Genealogy – Patronymic Naming

I have been working since late 2024 as manager of the Museum of Danish America’s Genealogy and Education Center on Main Street in Elk Horn, and I have had the privilege of doing lots of genealogy research. I have seen a lot of Danish names, and one thing that modern Americans sometimes struggle to wrap their heads around is patronymic names. 

In our modern American society, the common practice is that family surnames are passed down through the paternal line from generation to generation. So, my last name is Mortensen because my father’s last name was Mortensen. Also, women often will change their last name to that of their husband when they marry. People today take pride in their family name being passed down from generation to generation. 

Danish Americans do not usually have this heritage of a family name passed down through generations. It was only in the mid to late 19^th century that Danes adopted the tradition of passing on the father’s surname and changing a woman’s surname upon marriage. Prior to this, they used patronymic names, where a person’s surname is derived from their father’s first name. This was the norm in Scandinavian countries and is still used today in Iceland. The son of a man named Hans took the surname Hansen, and the daughter of a man named Hans took the surname Hansdatter. Women would not change their surname upon marriage – they would use the -datter surname throughout their life. 

Danish immigrants to America discontinued the use of patronymic names and adopted the family name system used in the United States. My great-great-grandfather Niels Mortensen was born in Denmark in 1844, immigrated to Iowa in the early 1870s, and was buried in the Elk Horn cemetery upon his passing. Niels’ father in Denmark was Morten Nielsen – Niels was the son of Morten. However, Niels was the first to pass Mortensen as a fixed family surname to his children. His son Philip, my great-grandfather, was named Philip Mortensen, not Philip Nielsen. 

This naming system makes Danish genealogy somewhat unique in that we are not usually tracing a family name through history. While my last name has now been used for five generations of Americans, having a last name such as Mortensen only means that somewhere in my family tree there was a man named Morten, and he had a son. Patronymic surnames only tell us the name of the person’s father, and 19^th century Danes mostly used a handful of names over and over – Hans, Anders, Rasmus, Jens, Niels, etc. – with the result that there are lots of people named Hansen, Andersen, Rasmussen, Jensen, Nielsen, in our Danish American communities today, as well as in Denmark. 

We take pride in these Danish names today because they signify our Danish heritage within the broad diversity of America. However, when examining our Danish ancestors in Denmark, these names were not so unique. There were likely multiple persons named Hans Rasmussen or Anne Jensdatter living in a small corner of Denmark over a short span of time. This makes it important to know places, dates, and relationships to other persons to be sure we are identifying the correct person. 

The Danes were fortunately good at keeping records – births, marriages, and deaths were recorded by the local parish church, and there was a government census every few years. Church records help distinguish people by listing a person’s parents, age, place of birth, or place of residence. Together these details of dates, places, and relationships help us determine if we have the right Hans Rasmussen. 

– Eric Mortensen, Genealogy Center Manager & Project Archivist