| Answer | Crossword Clue |
|---|---|
| NEB | The Missouri R. forms its eastern border |
| SDAK | The Missouri R. forms part of its border |
| NEBR | The Missouri R. forms part of its border |
| NEB | The Missouri R. forms part of its border |
| IND | The Ohio R. forms its southern border |
| ORE | The Snake R. forms part of its border |
| ALA | The Perdido R. forms part of its border |
| IDA | The Snake R. forms part of its border |
| ORE | The Columbia R. forms part of its border |
| ALA | The Chattahoochee R. forms part of its border |
| FLA | The Chattahoochee R. forms part of its border |
| ILL | The Wabash R. forms part of its border |
| ONT | The Pigeon R. forms part of its border |
| ORE | The Columbia R. forms much of its northern border |
| SDAK | The Big Sioux R. forms part of its border |
