Louisiana v. Mississippi

Background

Mississippi and Louisiana fought over about 2,000 acres along the Mississippi River near Lake Providence, where private landowners known as the Houston Group also claimed title. The dispute began as a quiet-title suit in federal court, moved through appeals, and returned here after this Court allowed Louisiana to file an original complaint and appointed a Special Master to gather evidence and recommend a decision.

Reasoning

The Court focused on whether the river boundary follows the main navigation channel (the “thalweg”) or whether an island exception applies. The Special Master found the disputed land came from Stack Island, which originally lay in Mississippi and later shifted toward Louisiana because of erosion and accretion. Applying the island exception—that a boundary set beside an island stays in place even if the main channel moves—the Special Master placed the boundary on the island’s west side. The Court agreed, rejecting Louisiana’s evidence that the island had vanished and accepting maps and witness testimony showing Stack Island’s continued existence. Because the land lies within Mississippi under that rule, Louisiana lacked a legal right to challenge the Houston Group’s private title.

Real world impact

The Court adopted the Special Master’s report, confirmed Mississippi’s control of the disputed area, and denied Louisiana’s request for a new hearing. The decision resolves ownership and the state boundary for this stretch of river. Private title claims supported by the Special Master remain in place, and the ruling relies on historical maps, testimony, and the longstanding island exception to the shifting-channel rule.