Wikipedia: Plymouth County, Iowa
- Encyclopedia article features geography, demographics and links to cities and towns. Includes maps.
- http://en.wikipedia.org/wiki/Plymouth_County,_Iowa

Plymouth County Conservation Board
- Manages over 2000 acres of recreational and natural lands. Includes calendar of events, area descriptions, rental fees and staff directory.
- http://www.plymouthcountyparks.com/

City-Data.com: Plymouth 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/Plymouth_County-IA.html

Plymouth County, Iowa - US Census Bureau
- Provides population, demographic, and housing information.
- http://quickfacts.census.gov/qfd/states/19/19149.html

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

Farmers Cooperative Company
- Provides service and product lines in grain, feed, agronomy and petroleum. Contains company profile, hours, grain policies, headlines and quotes. Located in Hinton, Akron, Oyens and West Le Mars.
- http://www.my-coop.com/

Plymouth County, Iowa
- Features its history, information about the board of supervisors, agenda, minutes, and departments.
- http://www.co.plymouth.ia.us/

Plymouth County Fair
- Held annually in July. Includes an events schedule, a directory of the Fair Board, and information about accommodations.
- http://www.plymouthcountyfair.org/