Founded in 1864, Ada County is one of 44 counties in the state of Idaho. Historically, Ada County was formed from Boise County. The city of Boise is the county seat. With FIPS code of 1, Ada County has a population of 511,931 and area of 1,055 square miles (2,732 km2).
List of all cities in Ada County, ID alphabetically
| City/Town | Postal Code | Area Code |
| Albertsons, ID | 83726 | 208 |
| Boise, ID | 83701 | 208 |
| 83702 | 208 | |
| 83703 | 208 | |
| 83704 | 208 | |
| 83705 | 208 | |
| 83706 | 208 | |
| 83707 | 208 | |
| 83708 | 208 | |
| 83709 | 208 | |
| 83711 | 208 | |
| 83712 | 208 | |
| 83713 | 208 | |
| 83714 | 208 | |
| 83715 | 208 | |
| 83716 | 208 | |
| 83717 | 208 | |
| 83719 | 208 | |
| 83720 | 208 | |
| 83722 | 208 | |
| 83724 | 208 | |
| 83725 | 208 | |
| 83726 | 208 | |
| 83728 | 208 | |
| 83729 | 208 | |
| 83731 | 208 | |
| 83732 | 208 | |
| 83735 | 208 | |
| 83756 | 208 | |
| 83799 | 208 | |
| Boise Cascade, ID | 83728 | 208 |
| Boise State University, ID | 83725 | 208 |
| Dept of Transportation, ID | 83731 | 208 |
| Eagle, ID | 83616 | 208 |
| Federal Building, ID | 83724 | 208 |
| Garden City, ID | 83703 | 208 |
| 83714 | 208 | |
| Hidden Springs, ID | 83714 | 208 |
| I D State Dept of Employ, ID | 83735 | 208 |
| Idaho State House, ID | 83720 | 208 |
| Idaho State Tax Commission, ID | 83722 | 208 |
| 83756 | 208 | |
| Intermountain Gas Co, ID | 83732 | 208 |
| Kuna, ID | 83634 | 208 |
| Mayfield, ID | 83716 | 208 |
| Meridian, ID | 83642 | 208 |
| 83646 | 208 | |
| 83680 | 208 | |
| Mora, ID | 83634 | 208 |
| Pearl, ID | 83616 | 208 |
| Star, ID | 83669 | 208 |
| Ustick, ID | 83704 | 208 |
| Washington Group, ID | 83729 | 208 |