Los Angeles County which has a population of 9,818,605. The county itself is more populous than 42 states.
The most populated county in the US is Los Angeles County in California with a total population of 9,878,554.
According to census.gov, the 2007 population estimate for Maricopa County, Arizona, is 3,880,181.
King County
According to census.gov, Milwaukee County, Wisconsin, has the most population at 951,252 people in 2007.
In area, Sweetwater County is the largest county in Wyoming with a total area of 10,491 square miles (27,172 km²), of which 10,425 square miles (27,001 km²) is land and 66 square miles (171 km²) (0.63%) is water. Sweetwater county is also the 8th largest county in the US. By population, the largest county in Wyoming is Laramie County with a population of 91,738 according to the 2010 US Census.
According to census.gov, Hennepin County, Minnesota, has the most population at 1,136,599 people.
There are 53 counties in North Dakota. Cass County is the most populous county in North Dakota with a population of 149,778 per the 2010 U.S. Census.
Cass County, with a population of 149,778 in the 2010 US Census, is the most populated county in North Dakota. The largest city in North Dakota, Fargo, and the fifth largest city, West Fargo, are both located in Cass County.Cass County, North Dakota. With a population of 123,138.
The smallest county by population in Wyoming is Niobrara County with 2,484 people (2010 US Census).
San Juan County which had a population of 558 at the time of the 2000 US Census. Silverton is the County Seat and 531 of the County residents live in Silverton. The only school in the county in 2006 had a student body of 53 in grades k to 12.
According to census.gov, Middlesex County, Massachusetts has the most population with 1,473,416 people in 2007.
According to census.gov, Ada County, Idaho, has the most population at 373,406 people in 2007.