NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

LOUISIANA v. MISSISSIPPI et al.

on exceptions to report of special master

No. 121, Orig. Argued October 3, 1995—Decided October 31, 1995

Louisiana's bill of complaint in this original action asks the Court, inter alia, to define the boundary between that State and Mississippi along a 7-mile stretch of the Mississippi River. The case is here on Louisiana's exceptions to the report of the Special Master appointed by the Court.

Held: Louisiana's exceptions are overruled. The case is controlled by the island exception to the rule of the thalweg. The latter rule specifies that the river boundary between States lies along the main downstream navigational channel, or thalweg, and moves as the channel changes with the gradual processes of erosion and accretion. The island exception to that rule provides that if there is a divided river flow around an island, a boundary once established on one side of the island remains there, even though the main downstream navigation channel shifts to the island's other side. Pursuant to the island exception, the Special Master placed the boundary here at issue on the west side of the area here in dispute, thereby confirming Mississippi's sovereignty over the area. The Master took that action after finding that the area derived from Stack Island, which had originally been within Mississippi's boundary before the river's main navigational channel shifted to the east of the island, but which, through erosion on its east side and accretion on its west side, changed from its original location, next to the river's Mississippi bank, to its current location, abutting the Louisiana bank. The Master's findings and conclusions are carefully drawn and well documented with compelling evidence, whereas Louisiana's theory of the case is not supported by the evidence. Pp. 3–6.

Exceptions overruled, and Special Master's report and proposed decree adopted.

Kennedy, J., delivered the opinion for a unanimous Court.