Ceir sawl Swydd Jefferson yn yr Unol Daleithiau:
- Jefferson County, Alabama
- Jefferson County, Arkansas
- Jefferson County, Colorado
- Jefferson County, Efrog Newydd
- Jefferson County, Florida
- Jefferson County, Georgia
- Jefferson County, Gorllewin Virginia
- Jefferson County, Idaho
- Jefferson County, Illinois
- Jefferson County, Indiana
- Jefferson County, Iowa
- Jefferson County, Kansas
- Jefferson County, Kentucky
- Jefferson Parish County, Louisiana
- Jefferson County, Missouri
- Jefferson County, Mississippi
- Jefferson County, Montana
- Jefferson County, Nebraska
- Jefferson County, Ohio
- Jefferson County, Oklahoma
- Jefferson County, Oregon
- Jefferson County, Pennsylvania
- Jefferson County, Tennessee
- Jefferson County, Texas
- Jefferson County, Washington
- Jefferson County, Wisconsin