Mississippi v. Arkansas

Background

Mississippi and Arkansas disputed the state boundary in the old bed of the Mississippi River at Spanish Moss Bend and Luna Bar. Mississippi filed an original action in 1970 to fix the line after private title litigation. The factual fight turned on whether Luna Bar formed slowly by accretion (gradual river buildup) or suddenly by avulsion (a rapid shift of the channel). The parties agreed that accretion would favor Mississippi and avulsion would favor Arkansas.

Reasoning

The Court reviewed the Special Master’s detailed fact-finding and independent record. The Master credited Mississippi’s expert witnesses and found support in historical river charts that showed Luna Bar as a barren sandbar in 1882 and 1894. Mississippi’s expert Dr. Kolb found the Arkansas bank about twelve feet higher than the bar, and the absence of pre-1860 levees on Luna Bar supported Mississippi’s theory. Arkansas conceded Mississippi had made a sufficient initial showing but failed to rebut it. The Court therefore affirmed the Special Master’s findings and entered a decree in favor of Mississippi.

Real world impact

The decision fixes the boundary in this local area and awards Luna Bar to Mississippi, resolving competing private title claims and guiding which State controls the land and waters there. The Court relied on factual findings rather than creating new legal rules about river changes. The decree settles this dispute, though the factual approach is specific to these circumstances.

Dissents or concurrances

Justice Douglas dissented, emphasizing evidence of ancient tree stumps, soil borings, elevations, and long-time local testimony suggesting Luna Bar was once part of Arkansas and severed by a violent avulsive event.