Here is a list of pairs of neighboring countries that have been at war with each other at some point between 1700 and 2000, where at least one section of their border is defined by a river or creek flowing approximately from East to West or from West to East. In each case, one country is to the north of the river/creek and the other is to the south:
1. **United States and Mexico**
- River: Rio Grande (Rio Bravo)
- Wars: Mexican-American


