| Term | Definition |
| Atlantic Ocean | Served as the highway for explorers, early settlers, and later immigrants |
| Pacific Ocean | Was an early exploration route |
| Great Lakes | Inland port cities grew around this body of water in the Midwest |
| Gulf of Mexico | Provided the French and Spanish with exploration routes to Mexico and other parts of America |
| Columbia River | Was explored by Lewis and Clark |
| Rio Grande River | Forms the border between Texas and Mexico |
| Mississippi and Missouri Rivers | Transportation arteries for farm and industrial products. Links to ports and other parts of the world |
| Ohio River | The gateway to the west |
| Colorado River | River explored by the Spanish |