Louisiana v. Mississippi
202 U.S. 1 (1906)

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U.S. Supreme Court

Louisiana v. Mississippi, 202 U.S. 1 (1906)

Louisiana v. Mississippi

No. 11, Original

Argued October 10, 11, 12, 1905

Decided March 5, 1906

202 U.S. 1


The act of Congress admitting Louisiana having given that state all islands within three leagues of her coast, and the subsequent act of Congress admitting Mississippi having purported to give that state all islands within six leagues of her shore, and some islands within nine miles of the Louisiana coast being also within eighteen miles of the Mississippi shore, although the apparent inconsistency is reconcilable, the basis of a boundary controversy involving to each state pecuniary values of magnitude, exists, and such a controversy between the two states in their sovereign capacity as states and having a boundary line separating them justifies the exercise of the original jurisdiction of this Court.

As the act admitting Mississippi was passed five years after the act admitting Louisiana, Congress could not take away any portion of Louisiana and give it to Mississippi. Section 3, Art. IV of the Constitution does not permit the claims of any particular state to be prejudiced by the exercise of the power of Congress therein conferred.

Acts of Congress passed at different times for the admission of different states where their respective subjects are not identical with or similar to each other do not form part of a homogeneous whole, of a common system, so as to allow a claimant under the later act to claim that it changed the earlier act by construction, and the rule of in pari materia does not apply.

Page 202 U. S. 2

The term thalweg is commonly used by writers on international law in the definition of water boundaries between states, meaning the middle or deepest or most navigable channel, and while often styled "fairway" or "midway" or "main channel," the word has been taken over into various languages, and the doctrine of the thalweg is often applicable in respect of water boundaries to sounds, bays, straits, gulfs, estuaries and other arms of the sea, and also applies to boundary lakes and land-locked seas whenever there is a deep water sailing channel therein.

The " maritime belt " is that part of the sea which, in contradistinction to the open sea, is under the sway of the riparian states.

As between the states of the Union, long acquiescence in the assertion of a particular boundary, and the exercise of sovereignty over the territory within it, should be accepted as conclusive, whatever the international rule may be in respect of the acquisition by prescription of large tracts of country claimed by two states.

The real, certain, and true boundary south of the Mississippi and north of the southeast portion of the Louisiana, and separating the two states in the waters of Lake Borgne, is the deep water channel sailing line emerging from the most eastern mouth of Pearl River into lake Borgne and extending through the northeast corner of Lake Borgne, north of Half Moon or Grand Island, thence east and south through Mississippi Sound, through South Pass between Cat Island and Isle a Pitre to the Gulf of Mexico.

The State of Louisiana, by leave of court, filed her bill against the State of Mississippi, October 27, 1902, to obtain a decree determining a boundary line between the two states, and requiring the State of Mississippi to recognize and observe the line so determined.

The bill alleged:

"1st. That the State of Louisiana was admitted into the Union of the United States of America by the act of Congress found in chapter 50 of the United States Statutes at Large, volume 2, page 701, approved April 6th, 1812, and therein the boundaries of the said State of Louisiana, in the preamble of said act, were described as follows:"

" Whereas the representatives of the people of all that part of the territory or country ceded under the name of 'Louisiana' by the treaty made at Paris on the 30th day of April, 1803, between the United States and France, contained within the following limits, that is to say, beginning at the mouth of the

Page 202 U. S. 3

River Sabine, thence by a line drawn along the middle of said river, including all islands to the 32d degree of latitude; thence due north to the northernmost part of the 33d degree of north latitude; thence along the said parallel of latitude to the River Mississippi; thence down the said river to the River Iberville, and from thence along the middle of said river and Lakes Maurepas and Pontchartrain to the Gulf of Mexico; thence bounded by the said gulf to the place of beginning, including all islands within three leagues of the coast,"


"2d. That, according to the foregoing description, the eastern boundary of the State of Louisiana was formed by the Mississippi River, beginning at the northeast corner of said state and extending south to the junction of the said river with the River Iberville (now known as Bayou Manchac), and thence extending eastwardly through the lower end of the Amite River, through the middle of Lake Maurepas, Pass Manchac, and Lake Pontchartrain, and, in order to reach the Gulf of Mexico, its only course was through the Rigolets, into Lake Borgne, and thence by the deep-water channel through the upper corner of Lake Borgne, following said channel, north of Half Moon Island, through Mississippi Sound to the north of Isle a Pitre, through the Cat Island channel, southwest of Cat Island, into the Gulf of Mexico, which said eastern boundary of the State of Louisiana is more fully shown on diagram No. 1, made part of this bill."

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