Crocker County is a defunct county in the U.S. state of Iowa. In 1870, the Iowa General Assembly created Crocker County from the northern part of Kossuth County. The county seat was located at Greenwood, Iowa. In December 1871, the Iowa Supreme Court declared the act creating this county a violation of the constitution, which in article eleven declares that no new county shall be created which contains less than 432 sqmi. As Crocker County was smaller than the law allowed for, it ceased to exist from and after the rendition of that decision and the twelve townships in its territory reverted to Kossuth County.

Attempts of re-establishment

On February 22, 1913, legislation was introduced again to create a new county in the northern area of Kossuth. The proposed region would be called Larrabee County. It was named after governor William Larrabee. The proposal failed after a referendum.