Calhoun County is a narrow finger of mostly high ground located between the Mississippi River and the Illinois River. It is serviced by two state operated free ferry boats crossing the Illinois River (the Brussels Ferry and the Kampsville ferry) and one privately operated toll ferry boat crossing the Mississippi River into Missouri (the Golden Eagle ferry). There is also one bridge that spans the Illinois River at Hardin as well as land routes to the north into bordering Pike County.
The county had many prosperous farms and orchards at a time when transportation was mainly by river. It is very popular with sight seers in the fall due to the natural beauty of the Illinois River valley and its proximity to the Great River Road. Calhoun County was added to the St. Louis Metropolitan Statistical Area in 2003, along with Bond and Macoupin counties in Illinois, and in Washington County, Missouri.
Calhoun County is home to the Center for American Archeology, located in Kampsville.
There were 2,046 households out of which 29.00% had children under the age of 18 living with them, 60.80% were married couples living together, 5.70% had a female householder with no husband present, and 29.70% were non-families. 26.50% 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 2.46 and the average family size was 2.98.
In the county the population was spread out with 22.90% under the age of 18, 7.60% from 18 to 24, 25.90% from 25 to 44, 24.40% from 45 to 64, and 19.20% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 100.80 males. For every 100 females age 18 and over, there were 100.40 males.
The median income for a household in the county was $34,375, and the median income for a family was $43,107. Males had a median income of $32,281 versus $20,943 for females. The per capita income for the county was $16,785. About 7.30% of families and 9.00% of the population were below the poverty line, including 9.10% of those under age 18 and 9.80% of those age 65 or over.