Illinois v. Missouri
Headline: Court fixes the precise Illinois–Missouri boundary along the Mississippi, confirms Illinois ownership of Kaskaskia and Beaver Islands, upholds Missouri ownership of two river islands, and splits costs equally.
Holding: The Court adopts the Special Master’s report, fixes the detailed Illinois–Missouri boundary, declares Kaskaskia and Beaver Islands belong to Illinois and Cottonwoods and Roth Island to Missouri, and has the parties split costs equally.
- Fixes which state governs Kaskaskia and Beaver Islands.
- Confirms Missouri ownership of Cottonwoods and Roth Island.
- Splits court costs equally between Illinois and Missouri.
Summary
Background
This case was sent to a Special Master, who filed a report, and the two States agreed on the form of a decree. The dispute involved the exact boundary line between Illinois and Missouri in a stretch of the Mississippi River and which state had territorial and sovereignty rights over several river islands named in the evidence: Kaskaskia Island, Beaver Island, Cottonwoods, and Roth Island.
Reasoning
The Court adopted the Special Master’s Findings of Fact and Conclusions of Law and entered a decree. The decree fixes the boundary by a detailed legal description of courses and distances along river centerlines (taken from the parties’ agreed Attachment "C"). The Court confirmed that Illinois holds the territorial and sovereignty rights to Kaskaskia Island and Beaver Island, and that Missouri holds the territorial and sovereignty rights to Cottonwoods and Roth Island. The decree states those islands lie on their respective sides of the fixed boundary so no separate descriptions are needed. The Court also ordered that the costs of the suit be split equally between the States.
Real world impact
The ruling determines which State governs each named island and clarifies territorial control in that river area. That affects which State’s laws, officials, and responsibilities apply on those islands. The clear, written boundary and the confirmed ownerships remove ambiguity about sovereignty in the specific area described in the decree.
Dissents or concurrances
Mr. Justice Blackmun did not take part in entering this decree, a fact the opinion records.
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