Wisconsin v. Michigan
Argued March 2, 1936
Decided March 16, 1936
Full case nameThe State of Wisconsin v. The State of Michigan
Citations297 U.S. 547 (more)
56 S. Ct. 584; 80 L. Ed. 856
Case history
Prior295 U.S. 455 (1935).
The boundary between Michigan and Wisconsin is amended as stated
Court membership
Chief Justice
Charles E. Hughes
Associate Justices
Willis Van Devanter · James C. McReynolds
Louis Brandeis · George Sutherland
Pierce Butler · Harlan F. Stone
Owen Roberts · Benjamin N. Cardozo
Case opinion
Disputed area
Disputed area
Disputed area
Ships passing between Green Bay (left) and Lake Michigan (right) traveled between various islands.
Disputed area
Disputed area
Disputed area (the United States)
Coordinates45°19′17″N 86°54′58″W / 45.321487°N 86.916073°W / 45.321487; -86.916073Coordinates: 45°19′17″N 86°54′58″W / 45.321487°N 86.916073°W / 45.321487; -86.916073
Total islands4: Detroit, Plum, Rock & Washington

Two Supreme Court cases, Wisconsin v. Michigan, 295 U.S. 455 (1935) and Wisconsin v. Michigan, 297 U.S. 547 (1936), settled a territorial dispute between Wisconsin and Michigan.


The 1836 boundary description between Wisconsin and Michigan described the line through northwest Lake Michigan as "the most usual ship channel". This description needed clarification as two routes were in use into Green Bay. Four islands lay in between and all were claimed as part of both Door County, Wisconsin, and Delta County, Michigan. A similar case, Michigan v. Wisconsin 270 U.S. 295 (1926), had previously been brought to the Supreme Court but was dismissed.


In 1936, the Supreme Court decision chose the northernmost ship channel as the more common, so Michigan lost the intervening water area and four islands: Plum, Detroit, Washington, and Rock.

See also