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About Plymouth County

Plymouth County is the westernmost county in the U.S. state of Iowa. As of the 2020 census, the population was 25,698, and was estimated to be 25,697 in 2025. The county seat and the largest city is Le Mars. Plymouth County was named after Plymouth, Massachusetts.

Description adapted from Wikipedia, CC BY-SA 4.0.

Plymouth County, Iowa
Plymouth County IA Courthouse — CC BY-SA 4.0, Scott Romine · source

History of Plymouth County

Plymouth County was formed on January 15, 1851. Settlement began in the county in 1856. In October 1859, the first courthouse was built in Melbourne, formerly located in the southeast quarter of section 34, Plymouth Township, about five to six miles due south of Merrill. The first public school opened its doors there with 32 pupils. In 1872 the county seat was moved to Le Mars and a courthouse and jail were built there in 1873. The present Plymouth County Courthouse was built in 1900 of red sandstone. During the Great Depression, farmers in the county organized the Farmers Holiday Group, to keep farm products off the market until the desired price was met. A radical group among them abducted Judge Bradley from his court chamber and threatened to hang him in the front of the courthouse.

Adapted from Wikipedia, CC BY-SA 4.0.

Plymouth County at a glance

County seat
Le Mars
Population
25,698 (2020)
Land area
864 sq mi
Founded
1851

Largest communities in Plymouth County

  1. Sioux City 85,797
  2. America Township 11,046
  3. Le Mars county seat 10,571
  4. Portland Township 1,851
  5. Hungerford Township 1,800

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Official channels

Plymouth County election resources

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Neighboring counties

Part of Iowa Voter Check

This is the Plymouth County page of Iowa Voter Check, a project of True the Vote, pointing Iowa voters at the official tools that already exist — and at Scan Check Protect to verify your registration.

Where anything here differs from what Plymouth County or the Iowa Secretary of State publishes, they are right and this page is not.