In the case of State of Georgia v. State of South Carolina in 1921, the Supreme Court was tasked with resolving a dispute over the boundary line between these two states along Savannah River. The controversy arose when both states claimed ownership over several islands within this river and its adjacent waters. The court had to determine whether certain islands belonged to Georgia or South Carolina based on colonial grants, historical possession, and other relevant evidence such as maps and documents from earlier periods. After considering all presented arguments and evidence, the Supreme Court ruled that most disputed areas were part of South Carolina's territory due to their location on its side of the main navigable channel (thalweg) which is often used as a natural boundary marker in international law for rivers serving as borders between jurisdictions.

In the dissenting opinion for the case of State of Georgia v. State of South Carolina, 1921, it was argued that there were significant errors in determining the boundary line between Georgia and South Carolina. The dissenting justices believed that historical documents and evidence had been misinterpreted or overlooked by the majority decision. They contended that a more accurate interpretation would place certain islands within Georgian territory rather than as part of South Carolina's jurisdiction as ruled by the court's majority decision. Furthermore, they disagreed with how river thalwegs (the deepest parts) were used to determine state boundaries when these could change over time due to natural processes such as erosion or sedimentation. In their view, this made them unreliable markers for permanent borders between states.