County License Plate Designators
| County Index | County | County Seat |
|---|---|---|
| 1A | Ada | Boise |
| 2A | Adams | Council |
| 1B | Bannock | Pocatello |
| 2B | Bear Lake | Paris |
| 3B | Benewah | St. Maries |
| 4B | Bingham | Blackfoot |
| 5B | Blaine | Hailey |
| 6B | Boise | Idaho City |
| 7B | Bonner | Sandpoint |
| 8B | Bonneville | Idaho Falls |
| 9B | Boundary | Bonners Ferry |
| 10B | Butte | Arco |
| 1C | Camas | Fairfield |
| 2C | Canyon | Caldwell |
| 3C | Caribou | Soda Springs |
| 4C | Cassia | Burley |
| 5C | Clark | Dubois |
| 6C | Clearwater | Orofino |
| 7C | Custer | Challis |
| E | Elmore | Mountain Home |
| 1F | Franklin | Preston |
| 2F | Fremont | St. Anthony |
| 1G | Gem | Emmett |
| 2G | Gooding | Gooding |
| I | Idaho | Grangeville |
| 1J | Jefferson | Rigby |
| 2J | Jerome | Jerome |
| K | Kootenai | Coeur d’Alene |
| 1L | Latah | Moscow |
| 2L | Lemhi | Salmon |
| 3L | Lewis | Nez Perce |
| 4L | Lincoln | Shoshone |
| 1M | Madison | Rexburg |
| 2M | Minidoka | Rupert |
| N | Nez Perce | Lewiston |
| 1O | Oneida | Malad City |
| 2O | Owyhee | Murphy |
| 1P | Payette | Payette |
| 2P | Power | American Falls |
| S | Shoshone | Wallace |
| 1T | Teton | Driggs |
| 2T | Twin Falls | Twin Falls |
| V | Valley | Cascade |
| W | Washington | Weiser |