List of counties in Illinois

There are 102 counties in the state of Illinois.  

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Old counties
 Dane County was renamed in 1840 to the current Christian County.
 The original Knox County, Illinois, became extinct with the formation of the Illinois Territory in 1809. It became Knox County, Indiana. The modern Knox County, Illinois was formed much later and was not a part of the original Knox County.

References

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Illinois
counties