The following counties satisfy your query:
| County | Population | County Seat | State | Links |
| Union County, AR | 45629 | El Dorado | Arkansas | View Public Records for Union County, AR |
| Union County, FL | 13442 | Lake Butler | Florida | View Public Records for Union County, FL |
| Union County, GA | 17289 | Blairsville | Georgia | View Public Records for Union County, GA |
| Union County, IL | 18293 | Jonesboro | Illinois | View Public Records for Union County, IL |
| Union County, IN | 7349 | Liberty | Indiana | View Public Records for Union County, IN |
| Union County, IA | 12309 | Creston | Iowa | View Public Records for Union County, IA |
| Union County, KY | 15637 | Morganfield | Kentucky | View Public Records for Union County, KY |
| Union County, LA | 22803 | Farmerville | Louisiana | View Public Records for Union County, LA |
| Union County, MS | 25362 | New Albany | Mississippi | View Public Records for Union County, MS |
| Union County, NJ | 522541 | Elizabeth | New Jersey | View Public Records for Union County, NJ |
| Union County, NM | 4174 | Clayton | New Mexico | View Public Records for Union County, NM |
| Union County, NC | 123677 | Monroe | North Carolina | View Public Records for Union County, NC |
| Union County, OH | 40909 | Marysville | Ohio | View Public Records for Union County, OH |
| Union County, OR | 24530 | La Grande | Oregon | View Public Records for Union County, OR |
| Union County, PA | 41624 | Lewisburg | Pennsylvania | View Public Records for Union County, PA |
| Union County, SC | 29881 | Union | South Carolina | View Public Records for Union County, SC |
| Union County, SD | 12584 | Elk Point | South Dakota | View Public Records for Union County, SD |
| Union County, TN | 17808 | Maynardville | Tennessee | View Public Records for Union County, TN |