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- Gila County, Arizona: Gila is named for the Gila River.
- Grand County, Colorado: Grand is named for the Grand River, later renamed the Colorado River.
- Grand County, Utah: Grand is named for the Grand River, later renamed the Colorado River.
- Greenbrier County, West Virginia: Greenbrier is named for the Greenbrier River.
Read more about this topic: List Of U.S. Counties Named After Rivers