| Otter Tail | 60,000 | Fergus Falls | Minnesota | Fargo, ND | View → |
| Ouachita | 22,000 | Camden | Arkansas | Little Rock, AR | View → |
| Ouachita | 160,000 | Monroe | Louisiana | Shreveport, LA | View → |
| Ouray | 5,000 | Ouray | Colorado | Denver-Colorado Springs, CO | View → |
| Outagamie | 192,000 | Appleton | Wisconsin | Green Bay, WI-Duluth, MN | View → |
| Overton | 22,500 | Livingston | Tennessee | Nashville, TN | View → |
| Owen | 10,700 | Owenton | Kentucky | Cincinnati-Dayton, OH | View → |
| Owen | 21,000 | Spencer | Indiana | Indianapolis-Fort Wayne, IN | View → |
| Owsley | 4,500 | Booneville | Kentucky | Lexington-Bowling Green, KY | View → |
| Owyhee | 12,000 | Homedale | Idaho | Boise-Pocatello, ID | View → |
| Oxford | 58,000 | South Paris | Maine | Portland-Bangor, ME | View → |
| Ozark | 9,300 | Gainesville | Missouri | Springfield, MO | View → |
| Ozaukee | 92,000 | Mequon | Wisconsin | Milwaukee, WI | View → |
| Pacific | 22,000 | Long Beach | Washington | Seattle, WA | View → |
| Page | 15,000 | Clarinda | Iowa | Omaha, NE-Sioux City, IA | View → |
| Page | 23,500 | Luray | Virginia | Washington, DC | View → |
| Palm Beach | 1,529,300 | West Palm Beach | Florida | Miami-West Palm Beach, FL | View → |
| Palo Alto | 8,900 | Emmetsburg | Iowa | Omaha, NE-Sioux City, IA | View → |
| Palo Pinto | 29,000 | Mineral Wells | Texas | Dallas-Fort Worth, TX | View → |
| Pamlico | 13,000 | Bayboro | North Carolina | Raleigh-Greenville-Wilmington, NC | View → |
| Panola | 35,000 | Batesville | Mississippi | Memphis, TN | View → |
| Panola | 24,000 | Carthage | Texas | Shreveport, LA | View → |
| Park | 20,000 | Fairplay | Colorado | Denver-Colorado Springs, CO | View → |
| Park | 17,000 | Livingston | Montana | Missoula-Billings-Butte, MT | View → |
| Park | 29,500 | Cody | Wyoming | Missoula-Billings-Butte, MT | View → |
| Parke | 17,000 | Rockville | Indiana | Indianapolis-Fort Wayne, IN | View → |
| Parker | 150,000 | Weatherford | Texas | Dallas-Fort Worth, TX | View → |
| Parmer | 9,500 | Farwell | Texas | Amarillo, TX | View → |
| Pasco | 631,200 | New Port Richey | Florida | Tampa, FL | View → |
| Pasquotank | 40,000 | Elizabeth City | North Carolina | Norfolk, VA-Salisbury, MD | View → |
| Passaic | 521,124 | Paterson | New Jersey | New York, NY | View → |
| Patrick | 18,000 | Stuart | Virginia | Roanoke-Harrisonburg, VA | View → |
| Paulding | 180,000 | Dallas | Georgia | Atlanta, GA | View → |
| Paulding | 18,000 | Paulding | Ohio | Indianapolis-Fort Wayne, IN | View → |
| Pawnee | 2,600 | Pawnee City | Nebraska | Omaha, NE-Sioux City, IA | View → |
| Pawnee | 16,500 | Pawnee | Oklahoma | Tulsa, OK-Fort Smith, AR | View → |
| Pawnee | 6,800 | Larned | Kansas | Wichita, KS | View → |
| Payette | 25,000 | Payette | Idaho | Boise-Pocatello, ID | View → |
| Payne | 83,000 | Stillwater | Oklahoma | Oklahoma City, OK | View → |
| Peach | 27,000 | Fort Valley | Georgia | Macon-Columbus, GA | View → |
| Pearl River | 56,000 | Picayune | Mississippi | New Orleans-Baton Rouge, LA | View → |
| Pecos | 16,000 | Fort Stockton | Texas | El Paso-Odessa, TX | View → |
| Pembina | 7,100 | Cavalier | North Dakota | Fargo, ND | View → |
| Pemiscot | 17,000 | Caruthersville | Missouri | Memphis, TN | View → |
| Pend Oreille | 14,000 | Newport | Washington | Spokane, WA | View → |
| Pender | 66,000 | Burgaw | North Carolina | Raleigh-Greenville-Wilmington, NC | View → |
| Pendleton | 14,500 | Falmouth | Kentucky | Cincinnati-Dayton, OH | View → |
| Pendleton | 7,000 | Franklin | West Virginia | Roanoke-Harrisonburg, VA | View → |
| Pennington | 14,500 | Thief River Falls | Minnesota | Fargo, ND | View → |
| Pennington | 120,000 | Rapid City | South Dakota | Sioux Falls-Rapid City, SD | View → |
