Rio Grande border disputes
The Rio Grande (Río Bravo del Norte) has changed course several times in recorded history, leading to a number of border disputes and uncertainties, both international (involving Mexico and the United States) and between individual U.S. states: The Country Club Dispute was a dispute between Texas and New Mexico. The U.S. Supreme Court resolved this dispute in 1927.
Source: Wikipedia — Rio Grande border disputes (CC BY-SA 4.0)