| 100% | ALABAMABORDER | 13 | The Chattahoochee River forms part of it |
| 78% | PERU | 4 | The Putumayo River forms part of its northern border |
| 72% | IOWA | 4 | The Big Sioux River forms part of its border |
| 70% | IOWA | 4 | The Mississippi and Missouri rivers form parts of its border |
| 64% | EMS | 3 | River forming part of the Germany-Netherlands boundary |
| 63% | ARAS | 4 | River forming part of the border between Azerbaijan and Iran |
| 63% | URAL | 4 | River forming part of the boundary between Europe and Asia |
| 63% | MOSELLE | 7 | River forming part of the border between Germany and Luxembourg |
| 63% | ENDPAPER | 8 | Part of it forms the flyleaf |
| 60% | ARG | 3 | The Iguazu Riv. forms part of its border |
| 59% | ODER | 4 | It forms part of the Polish/German border |
| 58% | OHIO | 4 | River forming the borders of parts of five states |
| 57% | DEE | 3 | River that forms part of the England/Wales boundary |
| 57% | GUADIANA | 8 | River that forms part of the Spain-Portugal border |
| 57% | RHINE | 5 | River that forms part of the France/Germany border |
| 57% | WABASH | 6 | River that forms part of the Illinois-Indiana border |
| 56% | NIAGARA | 7 | River that forms part of the U.S.-Canada border |
| 56% | ESTUARY | 7 | Wide part of a river where it meets the sea |
| 56% | ESTUARY | 7 | Lower part of a river where it meets the sea |
| 56% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with Belarus and Ukraine |
| 55% | ODER | 4 | River that forms part of the border between Germany and Poland |
| 55% | ORINOCO | 7 | River that forms part of the border between Colombia and Venezuela |
| 55% | MOSELLE | 7 | River that forms part of the border between Germany and Luxembourg |
| 55% | DOURO | 5 | River that forms part of the border between Spain and Portugal |
| 55% | RIONEGRO | 8 | River that forms part of the border between Colombia and Venezuela |
| 55% | BUG | 3 | Tributary of the Narew River forming part of Poland's border with both Belarus and Ukraine |
| 55% | ELBE | 4 | River that formed part of the border between East and West Germany |
| 54% | ALA | 3 | State where the Chattahoochee R. forms part of the border |
| 53% | MAMORE | 6 | River rising in the Andes that forms part of the Bolivia-Brazil border |
| 52% | BERMEJO | 7 | River of N Argentina forming part of the border with Bolivia |