Approximately 800 square miles.
Shelby County, TN is 784 sq mi (2,031 km²).
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.
Baldwin County, AL's area is 2,027 square miles.