Wikipedia: O'Brien County, Iowa
- Encyclopedia article highlights geography, demographics and links to localities. Contains maps.
- http://en.wikipedia.org/wiki/O'Brien_County,_Iowa

O'Brien County, Iowa - US Census Bureau
- Provides population, demographic, and housing information.
- http://quickfacts.census.gov/qfd/states/19/19141.html

Iowa State University Extension - O'Brien County
- Offers agricultural, business, family and 4-H programs and resources. Includes staff directory, news, events, hours and directions. Located in Primghar.
- http://www.extension.iastate.edu/obrien

O'Brien County Economic Development Corporation
- Features information about the business climate, communities and government of Northwest Iowa.
- http://www.obriencounty.com/

The Community Agency
- Joint venture between the cities of Hartley, Paullina, Primghar, and Sanborn. Began as a cable TV supplier, then added Internet access, most recently has begun to offer phone service.
- http://www.tcaexpress.com/