Osage County: 2,251 square miles.
Kossuth County is the largest county in Iowa by land area, covering approximately 973 square miles.
Cherokee County, Oklahoma covers approximately 749 square miles.
The largest is Berkeley County with 1,228 square miles.
The largest county in square miles in Kansas is Sedgwick County, with an area of approximately 998 square miles.
The largest is Nye County with 18,147 square miles.