Wikipedia: Sioux County, Iowa
- Encyclopedia article covers geography, demographics, politics and links to cities and towns. Includes maps.
- http://en.wikipedia.org/wiki/Sioux_County,_Iowa

City-Data.com: Sioux County, Iowa
- Profiles population demographics, jobs, housing, agriculture and crime statistics. Contains a list of recreational areas, churches, cemeteries, post offices, charts, graphs and maps.
- http://www.city-data.com/county/Sioux_County-IA.html

Historic Bridges of the U.S. : Bridges in Sioux County, Iowa
- Database provides overview, status, history and categories of five bridges in the county. Includes photographs.
- http://www.bridgehunter.com/ia/sioux/

Sioux County, Iowa - US Census Bureau
- Provides population, demographic, and housing information.
- http://quickfacts.census.gov/qfd/states/19/19167.html

Iowa State University Extension - Sioux County
- Offers agricultural, business, family and 4-H programs and resources. Includes staff directory, news, events, hours and directions. Located in Orange City.
- http://www.extension.iastate.edu/sioux/

National Register of Historical Places - Sioux County
- Provides a listing of properties, districts, and landmarks in the county. Includes architectural style and period of significance.
- http://www.historicdistricts.com/IA/Sioux/state.html

Sioux County Sheriff
- Features sheriff's profile and includes information about the patrol, corrections and civil divisions, criminal investigation and special units.
- http://www.siouxcountysheriff.com/

Sioux County
- Official site. Includes history, FAQs and contact information.
- http://www.siouxcounty.org/