| 100% | OHIORIVER | 9 | It forms Indiana's southern border |
| 65% | RIVERPO | 7 | It forms much of Lombardy's southern border |
| 55% | MEKONG | 6 | It forms Myanmar's border with Laos |
| 54% | ODER | 4 | It forms part of Germany's eastern border |
| 54% | ELBE | 4 | It formed part of East Germany's border |
| 47% | ODER | 4 | It forms part of the Polish/German border |
| 46% | IOWA | 4 | The Mississippi forms its eastern border |
| 45% | CHINA | 5 | Country on Mongolia's southern border |
| 42% | ZIMBABWE | 8 | Victoria Falls forms part of its border |
| 42% | NEB | 3 | The Missouri R. forms its eastern border |
| 42% | IOWA | 4 | The Mississippi River forms its eastern border |
| 42% | MEXICO | 6 | This puzzle's southern border? |
| 42% | SOIL | 4 | It forms Earth's pedosphere |
| 41% | ARG | 3 | The Iguazu Riv. forms part of its border |
| 41% | IOWA | 4 | Its eastern and western borders are formed entirely by rivers |
| 41% | IOWA | 4 | Its east and west borders are formed entirely by rivers |
| 40% | PERU | 4 | The Putumayo River forms part of its northern border |
| 40% | IOWA | 4 | The Big Sioux River forms part of its border |
| 40% | OHIO | 4 | Most of its 981-mile course forms state borders |
| 40% | OMAN | 4 | Country on Saudi Arabia's southern border |
| 40% | MINUET | 6 | It's done in the form of an S or a Z |
| 39% | IOWA | 4 | The Mississippi and Missouri rivers form parts of its border |
| 38% | OHIO | 4 | It's east of Indiana |
| 38% | OHIORIVER | 9 | It's formed in Pittsburgh |
| 38% | RHINE | 5 | It borders Liechtenstein's capital |
| 37% | FJORD | 5 | It's formed by a glacier |
| 37% | ONTARIO | 7 | It borders five U.S. states |
| 37% | THENORWEGIANSEA | 15 | It borders Iceland's eastern coast |
| 37% | NAVAJO | 6 | It borders Arizona's Apache County |
| 37% | OHIO | 4 | Indiana's smallest county or the river it touches |