Nevada
- Bullfrog County, Nevada, created from a small portion of Nye County, Nevada in 1987, reabsorbed in 1989. Population: 0.
- Ormsby County, Nevada, now independent city of Carson City
- Pautah County, California - created by the California legislature out of territory the state believed would be ceded to it north of Lake Tahoe, but which was given to Nevada. County never officially organized.
- Roop County, Nevada - Portions west of 120°W became Lassen County, California, remainder annexed by Washoe County, Nevada in 1883. Also known as Lake County.
Read more about this topic: List Of Former United States Counties