Denison is a city in Crawford County, Iowa, United States, along the Boyer River. The population was 8,298 at the 2010 census. It is the county seat of Crawford County.
Denison was laid out in 1856; the town was incorporated in 1875. Denison was named for its founder, J. W. Denison.
Denison is located at 42°1′2″N 95°21′4″W (42.017187, −95.351124).
According to the United States Census Bureau, the city has a total area of 6.57 square miles (17.02 km2), of which, 6.54 square miles (16.94 km2) is land and 0.03 square miles (0.08 km2) is water.
At the 2010 census there were 8,298 people, 2,816 households, and 1,866 families living in the city. The population density was 1,268.8 inhabitants per square mile (489.9/km2). There were 2,968 housing units at an average density of 453.8 per square mile (175.2/km2). The racial makeup of the city was 70.6% White, 2.3% African American, 0.6% Native American, 1.0% Asian, 0.2% Pacific Islander, 23.0% from other races, and 2.3% from two or more races. Hispanic or Latino of any race were 42.1%.
Of the 2,816 households 38.0% had children under the age of 18 living with them, 48.8% were married couples living together, 11.1% had a female householder with no husband present, 6.4% had a male householder with no wife present, and 33.7% were non-families. 28.1% of households were one person and 13.7% were one person aged 65 or older. The average household size was 2.75 and the average family size was 3.36.