Knox County which has Knoxville as its county seat has an area of about 526 square miles.
Jackson county is 100.6 square miles
Marquette County, Michigan is 3,425 square miles.
Onondaga County, NY is 806 square miles.
Darlington County, SC is 567 square miles.
Tillamook County, Oregon is 1,133 square miles.
Lincoln County is 4 831 square miles.
Hennepin County, Minnesota is 606 square miles.
Rockwall County: 129 square miles.
Fulton County, GA's area is 534.75 square miles.
Baldwin County, AL's area is 2,027 square miles.
Loudon County, TN: 247 square miles.Loudon County, VA: 521 square miles.
Fayette County, Tennessee is 706 square miles.