| Rank |
County |
Population (2012) |
| 1 |
Los Angeles County, California
|
9,962,789
|
| 2 |
Cook County, Illinois
|
5,231,351
|
| 3 |
Harris County, Texas
|
4,253,700
|
| 4 |
Maricopa County, Arizona
|
3,942,169
|
| 5 |
San Diego County, California
|
3,177,063
|
| 6 |
Orange County, California
|
3,090,132
|
| 7 |
MiamiDade County, Florida
|
2,591,035
|
| 8 |
Kings County, New York
|
2,565,635
|
| 9 |
Dallas County, Texas
|
2,453,843
|
| 10 |
Queens County, New York
|
2,272,771
|
| 11 |
Riverside County, California
|
2,268,783
|
| 12 |
San Bernardino County, California
|
2,081,313
|
| 13 |
King County, Washington
|
2,007,440
|
| 14 |
Clark County, Nevada
|
2,000,759
|
| 15 |
Tarrant County, Texas
|
1,880,153
|
| 16 |
Santa Clara County, California
|
1,837,504
|
| 17 |
Broward County, Florida
|
1,815,137
|
| 18 |
Wayne County, Michigan
|
1,792,365
|
| 19 |
Bexar County, Texas
|
1,785,704
|
| 20 |
New York County, New York
|
1,619,090
|
| 21 |
Alameda County, California
|
1,554,720
|
| 22 |
Philadelphia County, Pennsylvania
|
1,547,607
|
| 23 |
Middlesex County, Massachusetts
|
1,537,215
|
| 24 |
Suffolk County, New York
|
1,499,273
|
| 25 |
Sacramento County, California
|
1,450,121
|
| 26 |
Bronx County, New York
|
1,408,473
|
| 27 |
Palm Beach County, Florida
|
1,356,545
|
| 28 |
Nassau County, New York
|
1,349,233
|
| 29 |
Hillsborough County, Florida
|
1,277,746
|
| 30 |
Cuyahoga County, Ohio
|
1,265,111
|
| 31 |
Allegheny County, Pennsylvania
|
1,229,338
|
| 32 |
Oakland County, Michigan
|
1,220,657
|
| 33 |
Orange County, Florida
|
1,202,234
|
| 34 |
Franklin County, Ohio
|
1,195,537
|
| 35 |
Hennepin County, Minnesota
|
1,184,576
|
| 36 |
Fairfax County, Virginia
|
1,118,602
|
| 37 |
Travis County, Texas
|
1,095,584
|
| 38 |
Contra Costa County, California
|
1,079,597
|
| 39 |
Salt Lake County, Utah
|
1,063,842
|
| 40 |
Montgomery County, Maryland
|
1,004,709
|
| 41 |
St Louis County, Missouri
|
1,000,438
|
| 42 |
Pima County, Arizona
|
992,394
|
| 43 |
Fulton County, Georgia
|
977,773
|
| 44 |
Honolulu County, Hawaii
|
976,372
|
| 45 |
Mecklenburg County, North Carolina
|
969,031
|
| 46 |
Westchester County, New York
|
961,670
|
| 47 |
Milwaukee County, Wisconsin
|
955,205
|
| 48 |
Wake County, North Carolina
|
952,151
|
| 49 |
Fresno County, California
|
947,895
|
| 50 |
Shelby County, Tennessee
|
940,764
|
| 51 |
Fairfield County, Connecticut
|
933,835
|
| 52 |
DuPage County, Illinois
|
927,987
|
| 53 |
Pinellas County, Florida
|
921,319
|
| 54 |
Erie County, New York
|
919,086
|
| 55 |
Marion County, Indiana
|
918,977
|
| 56 |
Bergen County, New Jersey
|
918,888
|
| 57 |
Hartford County, Connecticut
|
897,259
|
| 58 |
Prince Georges County, Maryland
|
881,138
|
| 59 |
Duval County, Florida
|
879,602
|
| 60 |
New Haven County, Connecticut
|
862,813
|
| 61 |
Kern County, California
|
856,158
|
| 62 |
Macomb County, Michigan
|
847,383
|
| 63 |
Gwinnett County, Georgia
|
842,046
|
| 64 |
Ventura County, California
|
835,981
|
| 65 |
Collin County, Texas
|
834,642
|
| 66 |
El Paso County, Texas
|
827,398
|
| 67 |
San Francisco County, California
|
825,863
|
| 68 |
Middlesex County, New Jersey
|
823,041
|
| 69 |
Baltimore County, Maryland
|
817,455
|
| 70 |
Pierce County, Washington
|
811,681
|
| 71 |
Montgomery County, Pennsylvania
|
808,460
|
| 72 |
Hidalgo County, Texas
|
806,552
|
| 73 |
Worcester County, Massachusetts
|
806,163
|
| 74 |
Hamilton County, Ohio
|
802,038
|
| 75 |
Essex County, New Jersey
|
787,744
|
| 76 |
Multnomah County, Oregon
|
759,256
|
| 77 |
Essex County, Massachusetts
|
755,618
|
| 78 |
Jefferson County, Kentucky
|
750,828
|
| 79 |
Monroe County, New York
|
747,813
|
| 80 |
Suffolk County, Massachusetts
|
744,426
|
| 81 |
Oklahoma County, Oklahoma
|
741,781
|
| 82 |
San Mateo County, California
|
739,311
|
| 83 |
Snohomish County, Washington
|
733,036
|
| 84 |
Cobb County, Georgia
|
707,442
|
| 85 |
Denton County, Texas
|
707,304
|
| 86 |
DeKalb County, Georgia
|
707,089
|
| 87 |
San Joaquin County, California
|
702,612
|
| 88 |
Lake County, Illinois
|
702,120
|
| 89 |
Will County, Illinois
|
682,518
|
| 90 |
Norfolk County, Massachusetts
|
681,845
|
| 91 |
Jackson County, Missouri
|
677,377
|
| 92 |
Bernalillo County, New Mexico
|
673,460
|
| 93 |
Jefferson County, Alabama
|
660,009
|
| 94 |
Hudson County, New Jersey
|
652,302
|
| 95 |
Davidson County, Tennessee
|
648,295
|
| 96 |
Lee County, Florida
|
645,293
|
| 97 |
El Paso County, Colorado
|
644,964
|
| 98 |
Denver County, Colorado
|
634,265
|
| 99 |
District of Columbia, District Of Columbia
|
632,323
|
| 100 |
Monmouth County, New Jersey
|
629,384
|