The largest County in Maine is Aroostook, measuring 6,829 square miles.
Putnam County, Florida has a total area of 827 square miles.
Idaho County is 8,502 sq miles (22,020 km²).
Harney County, OR is 10,226 sq miles (26,485 km²).
Riverside County, CA's area is 7,303.1 square miles.
The biggest county in the United States is San Bernardino County in California, covering approximately 20,105 square miles.
San Bernardino County covers approximately 20,105 square miles, which is equivalent to 12,868,912 acres.
There is no strict definition of "Southern California." But if you want to count LA County, San Diego County, Orange County, Riverside County, San Bernardino County, Ventura County, and Santa Barbara County; then Southern California is about 40,892 square miles. If you add in Kern County, San Luis Obispo County, and Imperial County...then Southern California is about 56,512 square miles.
There are 2,569 square miles in Lincoln County, Nevada.
The smallest county in Texas is Rockwall County, which is about 147 square miles in size.
Jackson County in Florida covers approximately 917 square miles.
Onondaga County, NY is 806 square miles.
Marquette County, Michigan is 3,425 square miles.
Darlington County, SC is 567 square miles.
Hennepin County, Minnesota is 606 square miles.
Tillamook County, Oregon is 1,133 square miles.
Fulton County, GA's area is 534.75 square miles.