In the 1933 case Vermont v. New Hampshire, the U.S. Supreme Court was tasked with resolving a boundary dispute between the two states that had been ongoing since colonial times. The disagreement centered around whether the western bank or middle of Connecticut River should serve as their border line. After reviewing historical documents and treaties, including one from King George II in 1740 which declared that "the west bank of Connecticut river...be forever hereafter reputed and remain to be the boundary line", Justice Benjamin N Cardozo ruled unanimously in favor of New Hampshire's claim to all islands on its side up until low water mark on Vermont’s side (western edge). This decision established a clear demarcation point for future reference, ending centuries-old territorial disputes between these neighboring states.

In the dissenting opinion for Vermont v. New Hampshire, 1933, it was argued that the majority's decision to grant New Hampshire jurisdiction over the Connecticut River up to its western bank did not accurately reflect historical precedent or original intent. The dissenters believed that both states had historically shared jurisdiction of the river and this should continue. They pointed out that many early charters and documents referred to Vermont’s eastern boundary as being in or along with the river rather than on its western bank. Furthermore, they noted a number of instances where Vermont exercised authority over islands in the river which would be inconsistent if their territory only extended up to its west bank. Therefore, according to them, there was no clear evidence supporting exclusive control by either state but rather suggested joint sovereignty over these waters.