Allen County (county code AL) is a county located in southeast portion of the U.S. state of Kansas. It is 504 square miles, or 322,560 acres in size. As of the 2010 census, the population was 13,371. Its county seat and most populous city is Iola.
According to the U.S. Census Bureau, the county has a total area of 505 square miles (1,310 km), of which 500 square miles (1,300 km) is land and 5.0 square miles (13 km) (1.0%) is water. Allen County is located in the southeastern part of the state, in the second tier of counties west of Missouri, and about fifty miles north of Oklahoma. In extent it is twenty-one miles from north to south and twenty-four miles from east to west.
As of the 2010 United States Census, there were 13,371 people residing in the county. 93.3% were White, 1.9% Black or African American, 0.8% Native American, 0.5% Asian, 1.0% of some other race and 2.5% of two or more races. 2.9% were Hispanic or Latino (of any race). 31.7% were of German, 12.4% American, 11.1% Irish and 7.9% English ancestry.
As of the 2000 census, there were 14,385 people, 5,775 households, and 3,892 families residing in Allen County. The population density was 29 people per square mile (11/km²). There were 6,449 housing units at an average density of 13 per square mile (5/km²). The racial makeup of the county was 94.80% White, 1.63% Black or African American, 0.78% Native American, 0.26% Asian, 0.86% from other races, and 1.68% from two or more races. Hispanic or Latino of any race were 1.93% of the population. 28.8% were of German, 20.3% American, 9.8% English and 8.6% Irish ancestry.
There were 5,775 households out of which 29.80% had children under the age of 18 living with them, 54.60% were married couples living together, 8.90% had a female householder with no husband present, and 32.60% were non-families. 28.50% of all households were made up of individuals and 14.40% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.98.
In the county, the population was spread out with 25.20% under the age of 18, 9.80% from 18 to 24, 24.10% from 25 to 44, 22.90% from 45 to 64, and 18.00% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 95.60 males. For every 100 females age 18 and over, there were 90.70 males.
The median income for a household in the county was $31,481, and the median income for a family was $39,117. Males had a median income of $27,305 versus $19,221 for females. The per capita income for the county was $15,640. About 11.30% of families and 14.90% of the population were below the poverty line, including 20.20% of those under age 18 and 12.70% of those age 65 or over.
During the years of the American Civil War the county continued to develop though at a slower rate. From 1860 to 1870 there was a steady increase in population from 3,082 to 7,022 residents. The next ten years brought a similar steady rise, from 7,022 to 11,303 residents. The county’s largest growth period was between 1890 and 1910. At its peak in 1910, Allen County had 27,640 residents. Thereafter the county experienced a slow decline in population. By 2010, the population was slightly below the population in 1890 there being 13,371 residents. The population increase during the 1890/1910 period was likely due to the oil and gas discoveries and production near Iola.