According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is the smallest county by land area in Iowa, and the fifth-smallest by total area. A region known as the Iowa Great Lakes is in Dickinson County, making it a popular vacation destination for Iowans, and explaining the recent high population growth in the area. The lakes include West Okoboji Lake, East Okoboji Lake, and Spirit Lake.
The 2010 census recorded a population of 16,667 in the county, with a population density of. There were 12,849 housing units, of which 7,554 were occupied.
2000 census
As of the census of 2000, there were 16,424 people, 7,103 households, and 4,759 families residing in the county. The population density was 43 people per square mile. There were 11,375 housing units at an average density of 30 per square mile. The racial makeup of the county was 98.90% White, 0.18% Black or African American, 0.21% Native American, 0.18% Asian, 0.01% Pacific Islander, 0.10% from other races, and 0.43% from two or more races. 0.66% of the population were Hispanic or Latino of any race. There were 7,103 households out of which 26.10% had children under the age of 18 living with them, 57.80% were married couplesliving together, 6.70% had a female householder with no husband present, and 33.00% were non-families. 28.60% of all households were made up of individuals and 13.70% had someone living alone who was 65 years of age or older. The average household size was 2.27 and the average family size was 2.78. In the county, the population was spread out with 21.90% under the age of 18, 6.60% from 18 to 24, 23.90% from 25 to 44, 26.90% from 45 to 64, and 20.60% who were 65 years of age or older. The median age was 43 years. For every 100 females, there were 95.00 males. For every 100 females age 18 and over, there were 92.30 males. The median income for a household in the county was $39,020, and the median income for a family was $47,739. Males had a median income of $30,523 versus $22,131 for females. The per capita income for the county was $21,929. 6.00% of the population and 4.20% of families were below the poverty line. Out of the total people living in poverty 5.90% of those under the age of 18 and 7.00% of those 65 and older were living below the poverty line.
