The largest county in Missouri by population is st. Louis
Marion County has the largest county population in Indiana.
Aroostook County is a county located in the U.S. state of Maine. In 2000, its population was 73,938. It is the largest county in the state. Its seat is Houlton.[1] In land area, Aroostook County is...
Cook County is the largest, by far, containing the City of Chicago. For further info, check out the Encyclopedia Brittanica or Wikipedia.
Fulton