Most of the counties are named after Meriwether Lewis.
- one of 44 counties in Idaho, USA, with its county seat in Nezperce.
- one of 120 counties in Kentucky, USA, the county seat is Vanceburg.
- one of 114 counties in Missouri, USA, the county seat is Monticello.
- one of 62 counties in New York, USA, the county seat is Lowville. Named after Morgan Lewis.
- one of 95 counties in Tennessee, USA, the county seat is Hohenwald.
- one of 39 counties in Washington USA, the county seat is Chehalis.
- one of 55 counties in West Virginia, USA, the county seat is Weston. Origin of name unknown.