The St. Ansgar church, congregation and town served as a center for the dispersion of Norwegian settlers north across the border into Minnesota and on into western Iowa from the mid-1850s into the late 1870s. Clausen formed 21 additional congregations. St.Ansgar First Lutheran, a graceful building constructed of limestone quarried from the banks of the nearby Cedar River and native hardwoods, is the oldest continuously active Lutheran congregation west of the Mississippi (Booklet published by the First Lutheran Church of St. Ansgar on the occasion of the 150th anniversary of the congregation, 1853-2003; available in the Iowa State Historical Society collection, IowaCity, IA, and at the church.)
Pastors in the National Church of Norway received university training in census record keeping; the current parish keeps copies of congregration records continuously from founding to the present, making these records a significant genealogical resource.
A fortified stone outbuilding locally called Fort Severson, one half mile west of St. Ansgar (on a gravel side road; signage is only on hardsurface state highway 105), was built in 1867 by settlers associated with the Clausen settlement anxious about the continued presence of Sauk and Fox Native Americans travelling through the area along the Deer Creek and the Cedar River. The settlers fears were animated by the killing of settlers at Spirit Lake Iowa in 1857 and in New Ulm, Minnesota in 1862. The distinctively fortified building, which functioned both as a barn and a fort, is the sole surviving example of many that were built. The site is open to the public, albeit requiring of persistence to find. (See St. Ansgar home page.)
There were 447 households out of which 21.7% had children under the age of 18 living with them, 55.0% were married couples living together, 6.0% had a female householder with no husband present, and 36.7% were non-families. 34.0% of all households were made up of individuals and 22.1% had someone living alone who was 65 years of age or older. The average household size was 2.13 and the average family size was 2.70.
In the city the population was spread out with 17.9% under the age of 18, 6.0% from 18 to 24, 19.8% from 25 to 44, 24.9% from 45 to 64, and 31.3% who were 65 years of age or older. The median age was 50 years. For every 100 females there were 77.8 males. For every 100 females age 18 and over, there were 74.4 males.
The median income for a household in the city was $33,977, and the median income for a family was $46,667. Males had a median income of $28,704 versus $20,294 for females. The per capita income for the city was $16,100. About 6.6% of families and 9.3% of the population were below the poverty line, including 15.6% of those under age 18 and 3.9% of those age 65 or over.