In the 1972 case of Nebraska v. Iowa, the U.S. Supreme Court was tasked with resolving a border dispute between the two states. The conflict arose due to changes in the course of Missouri River, which serves as their shared boundary line. Over time, accretion and avulsion had caused shifts in its path that led to confusion over land ownership rights on certain tracts along its banks. After reviewing historical documents and treaties related to state boundaries and river navigation laws, including an 1892 decision by itself concerning this same boundary issue (Nebraska v Iowa), the court ruled in favor of Iowa for most part of disputed territory except one tract known as McKissick's Island where it favored Nebraska based on evidence presented about nature of change being gradual or sudden (accretion vs avulsion). This ruling reaffirmed that when a river serving as a boundary changes gradually through natural processes like erosion or sediment deposition (accretion), new lands belong to owner whose bank they attach but if change is sudden due to events like flood or channel cutoffs (avulsion) then original property lines remain intact even if watercourse has shifted elsewhere.

The dissenting opinion in the case of Nebraska v. Iowa, 1972, argued that the majority's decision to uphold a previous ruling defining the boundary between Nebraska and Iowa was incorrect. The dissenters believed that this earlier decision had been based on an inaccurate understanding of historical events and documents related to the establishment of this border. They contended that new evidence presented during this case demonstrated clearly where the original boundary line should have been drawn according to treaties with Native American tribes and early government surveys. Therefore, they felt it was unjust for landowners who had long considered themselves residents of one state to suddenly find themselves living in another due solely to legal technicalities rather than any actual change in geographical circumstances or local consensus about state lines.