| Answer | Crossword Clue |
|---|---|
| OHIO | State, or river that forms its southern border |
| ILLINOIS | The Ohio River forms its southern border |
| IND | The Ohio R. forms its southern border |
| ONTARIO | The Detroit River forms part of its border |
| OREGON | The Columbia River forms much of its northern border |
| PERU | The Putumayo River forms part of its northern border |
| IOWA | The Big Sioux River forms part of its border |
