St. Olaf, Iowa  St. Olaf is a city in Clayton County, Iowa, United States. The population was 108 at the 2010 census, down from 136 in 2000. Swiss Valley has a large cheese packaging plant in St. Olaf.  St. Olaf was founded in 1872 and was incorporated as a town in 1900. Olaf is located at (42.927724, −91.387236). According to the United States Census Bureau, the city has a total area of , all land. As of the census of 2010, there were 108 people, 43 households, and 34 families living in the city. The population density was . There were 48 housing units at an average density of . The racial makeup of the city was 100.0% White. There were 43 households of which 27.9% had children under the age of 18 living with them, 67.4% were married couples living together, 11.6% had a female householder with no husband present, and 20.9% were non-families. 18.6% of all households were made up of individuals and 9.3% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 2.85. The median age in the city was 41 years. 25% of residents were under the age of 18; 7.5% were between the ages of 18 and 24; 22.2% were from 25 to 44; 27.8% were from 45 to 64; and 17.6% were 65 years of age or older. The gender makeup of the city was 47.2% male and 52.8% female. As of the census of 2000, there were 136 people, 49 households, and 39 families living in the city. The population density was 550.8 people per square mile (210.0/km²). There were 54 housing units at an average density of 218.7 per square mile (83.4/km²). The racial makeup of the city was 100.00% White. There were 49 households out of which 46.9% had children under the age of 18 living with them, 63.3% were married couples living together, 8.2% had a female householder with no husband present, and 18.4% were non-families. 14.3% of all households were made up of individuals and 14.3% had someone living alone who was 65 years of age or older.