The following is a sortable table of the most populous county in each U.S. state, federal district, and territory. Counties and states/territories in bold have a population of at least 1 million.
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Table
{| class="wikitable sortable"
|-
! State,<br>federal district,<br>or territory
! Largest county,<br>parish,<br>or municipality || 31,819|| — || 46,765 || 68.04%
|-
| || Maricopa || 4,673,096 || Phoenix || 7,582,384 || 61.63%
|-
| || Pulaski || 401,209 || Little Rock || 3,088,354 || 12.99%
|-
| || Los Angeles || 9,757,179 || Los Angeles || 39,431,263 || 24.74%
|-
| || El Paso || 752,772 || Colorado Springs || 5,957,493 || 12.64%
|-
| || Capitol || 991,508 || Hartford || 3,675,069 || 26.98%
|-
| || New Castle || 588,093 || Wilmington || 1,051,917 || 55.91%
|-
| || District of Columbia || 702,250 || District of Columbia || 702,250 || 100.00%
|-
| || Miami-Dade || 2,838,461 || Miami || 23,372,215 || 12.14%
|-
| Georgia || Fulton || 1,090,354 || Atlanta || 11,180,878 || 9.75%
|-
| || Guam || 943 || Hagåtña || 167,777 || 0.56%
|-
| || Honolulu || 998,747 || Honolulu || 1,446,146 || 69.06%
|-
| || Ada || 535,799 || Boise || 2,001,619 || 26.77%
|-
| || Cook || 5,182,617 || Chicago || 12,710,158 || 40.78%
|-
| || Marion || 981,628 || Indianapolis || 6,924,275 || 14.18%
|-
| || Polk || 516,185 || Des Moines || 3,241,488 || 15.92%
|-
| || Johnson || 632,276 || Olathe || 2,970,606 || 21.28%
|-
| || Jefferson || 793,881 || Louisville || 4,588,372 || 17.30%
|-
| || East Baton Rouge || 453,022 || Baton Rouge || 4,597,740 || 9.85%
|-
| || Cumberland || 313,809 || Portland || 1,405,012 || 22.33%
|-
| || Montgomery || 1,082,273 || Rockville || 6,263,220 || 17.28%
|-
| || Middlesex || 1,668,956 || Cambridge and Lowell || 7,136,171 || 23.39%
|-
| || Wayne || 1,771,063 || Detroit || 10,140,459 || 17.47%
|-
| || Hennepin || 1,273,334 || Minneapolis || 5,793,151 || 21.98%
|-
| || Harrison || 213,730 || Biloxi and Gulfport || 2,943,045 || 7.26%
|-
| || St. Louis || 992,929 || Clayton || 6,245,466 || 15.90%
|-
| || Yellowstone || 171,583 || Billings || 1,137,233 || 15.09%
|-
| || Douglas || 601,158 || Omaha || 2,005,465 || 29.98%
|-
| || Clark || 2,398,871 || Las Vegas || 3,267,467 || 73.42%
|-
| || Hillsborough || 430,462 || Manchester and Nashua || 1,409,032 || 30.55%
|-
| || Bergen || 978,641 || Hackensack || 9,500,851 || 10.30%
|-
| || Bernalillo || 671,747 || Albuquerque || 2,130,256 || 31.53%
|-
| New York || Kings || 2,617,631 || Brooklyn || 19,867,248 || 13.18%
|-
| || Wake || 1,232,444 || Raleigh|| 11,046,024 || 11.16%
|-
| || Cass || 200,945 || Fargo || 796,568 || 25.23%
|-
| || Saipan || 1,356,303 || Columbus|| 11,883,304 || 11.41%
|-
| || Oklahoma || 816,490 || Oklahoma City || 4,095,393 || 19.94%
|-
| || Multnomah || 795,897 || Portland || 4,272,371 || 18.63%
|-
| || Philadelphia || 1,573,916 || Philadelphia || 13,078,751 || 12.03%
|-
| || San Juan