The U.S. Supreme Court case State of Minnesota v. State of Wisconsin in 1919 was a dispute over the boundary line between the two states, specifically regarding an area known as the Dalles of St. Croix River and its surrounding islands. The disagreement arose due to different interpretations of treaties with Native American tribes that had originally defined state boundaries in this region during early U.S history. The court ruled in favor of Wisconsin, deciding that all islands lying within the main channel's thread (the deepest part) belonged to Wisconsin while those outside it were considered part of Minnesota territory based on historical evidence and previous legal precedents related to river boundaries between states.

In the dissenting opinion for the case of State of Minnesota v. State of Wisconsin, Justice Holmes disagreed with the majority's decision to grant Minnesota permission to file a bill in equity against Wisconsin over disputed boundary waters. He argued that there was no substantial controversy between the two states and therefore, it was not necessary for this issue to be resolved by the Supreme Court. According to him, both states had already agreed on their boundaries through previous legislation and treaties which were approved by Congress. Furthermore, he stated that any disputes regarding individual rights or properties within these areas should be handled by local courts rather than escalating them directly to federal level without proper cause.