Clay County is the name of 18 counties in the United States. Most are named for Henry Clay, U.S. Senator and statesman:
* Clay County, Alabama
* Clay County, Arkansas (named for John Clayton, and originally named Clayton County)
* Clay County, Florida
* Clay County, Georgia
* Clay County, Illinois
* Clay County, Indiana
* Clay County, Iowa (named for Henry Clay Jr., son of Henry Clay and a soldier in the Mexican–American War)
* Clay County, Kansas
* Clay County, Kentucky (named for Green Clay, cousin of Henry Clay, a member of the Kentucky state legislature)
* Clay County, Minnesota
* Clay County, Mississippi
* Clay County, Missouri
* Clay County, Nebraska
* Clay County, North Carolina
* Clay County, South Dakota
* Clay County, Tennessee
* Clay County, Texas
* Clay County, West Virginia
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County name disambiguation pages