At the 2000 census there were 11,771 people, 4,886 households, and 3,258 families in the county.
 The population density was 28 people per square mile (11/km²).
 There were 5,399 housing units at an average density of 13 per square mile (5/km²).
 The racial makeup of the county was 98.20% White, 0.08% Black or African American, 0.35% Native American, 0.25% Asian, 0.01% Pacific Islander, 0.68% from other races, and 0.44% from two or more races.
 1.30%.
were Hispanic or Latino of any race.

Of the 4,886 households 29.70% had children under the age of 18 living with them, 54.40% were married couples living together, 8.70% had a female householder with no husband present, and 33.30% were non-families.
29.50% of households were one person and 14.70% were one person aged 65 or older.
 The average household size was 2.36 and the average family size was 2.91.

The age distribution was 25.00% under the age of 18, 6.50% from 18 to 24, 25.50% from 25 to 44, 22.80% from 45 to 64, and 20.30% 65 or older.
 The median age was 40 years.
For every 100 females there were 90.20 males.
 For every 100 females age 18 and over, there were 87.30 males.

The median household income was $33,214 and the median family income  was $40,129.
Males had a median income of $28,531 versus $20,835 for females.
The per capita income for the county was $16,373.
 About 6.50% of families and 9.10% of the population were below the poverty line, including 12.30% of those under age 18 and 6.00% of those age 65 or over.
At the 2000 census there were 11,771 people, 4,886 households, and 3,258 families in the county.  The population density was 28 people per square mile (11/km²).  There were 5,399 housing units at an average density of 13 per square mile (5/km²).  The racial makeup of the county was 98.20% White, 0.08% Black or African American, 0.35% Native American, 0.25% Asian, 0.01% Pacific Islander, 0.68% from other races, and 0.44% from two or more races.  1.30%. were Hispanic or Latino of any race.
Of the 4,886 households 29.70% had children under the age of 18 living with them, 54.40% were married couples living together, 8.70% had a female householder with no husband present, and 33.30% were non-families. 29.50% of households were one person and 14.70% were one person aged 65 or older.  The average household size was 2.36 and the average family size was 2.91.
The age distribution was 25.00% under the age of 18, 6.50% from 18 to 24, 25.50% from 25 to 44, 22.80% from 45 to 64, and 20.30% 65 or older.  The median age was 40 years. For every 100 females there were 90.20 males.  For every 100 females age 18 and over, there were 87.30 males.
The median household income was $33,214 and the median family income  was $40,129. Males had a median income of $28,531 versus $20,835 for females. The per capita income for the county was $16,373.  About 6.50% of families and 9.10% of the population were below the poverty line, including 12.30% of those under age 18 and 6.00% of those age 65 or over.
Montgomery County, Iowa