According to the U.S. Census Bureau, the county has a total area of 413 square miles (1,070 km2), of which 408 square miles (1,060 km2) is land and 4.8 square miles (12 km2) (1.2%) is water. It is the fifth-smallest county in Minnesota by land area and fourth-smallest by total area.
Native vegetation based on NRCS soils information
In recent years, average temperatures in the county seat of Foley have ranged from a low of 2 °F (−17 °C) in January to a high of 82 °F (28 °C) in July, although a record low of −43 °F (−42 °C) was recorded in January 1977 and a record high of 107 °F (42 °C) was recorded in July 1936. Average monthly precipitation ranged from 0.62 inches (16 mm) in February to 4.17 inches (106 mm) in June.
There were 13,065 households out of which 35.30% had children under the age of 18 living with them, 52.10% were married couples living together, 8.80% had a female householder with no husband present, and 34.80% were non-families. 25.80% of all households were made up of individuals and 8.90% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.14.
In the county the population was spread out with 27.10% under the age of 18, 12.20% from 18 to 24, 31.00% from 25 to 44, 18.70% from 45 to 64, and 11.00% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 99.60 males. For every 100 females age 18 and over, there were 96.30 males.
The median income for a household in the county was $41,968, and the median income for a family was $51,277. Males had a median income of $33,214 versus $22,737 for females. The per capita income for the county was $19,008. About 4.50% of families and 7.10% of the population were below the poverty line, including 6.30% of those under age 18 and 12.60% of those age 65 or over.