Mr. Justice Blackmun
delivered the opinion: of the Court.
Almost seven years ago, in March 1966, the State of Ohio instituted this original action against the Commonwealth of Kentucky. By its prayer for relief in its proposed bill of complaint, Ohio asked only that the Court declare and establish:
“1. The boundary line between the State of Ohio and the State of Kentucky as being the low water mark on the northerly side of the Ohio River in the year 1792 ....
“2. The State of Ohio and the State of Kentucky have equal and concurrent jurisdiction over and on all of the Ohio River from the northerly shore to the Southerly shore, except jurisdiction incidental to the sovereignty of the soil under the river and structures permanently attached thereto.”
In its complaint Ohio alleged:
“4. The State of Ohio was established from the land ceded by legislative act of the Commonwealth of Virginia to the United States on the 1st day of March, 1784, which act is known as the Cession of Virginia.
“5. The State of Kentucky was established by the separation of the District of Kentucky from the jurisdiction of the Commonwealth of Virginia pursuant to that certain act of the Virginia Legislature entitled 'An Act concerning the erection of the district of Kentucky into an independent state/ passed on the 18th day of December, 1789, which act is known as the Virginia-Kentucky Compact.
“6. The northern boundary line of the State of Kentucky was established from the Cession of Virginia and the Virginia-Kentucky Compact as the low water mark on the northerly side of the Ohio River as it existed in the year 1792.”
Ohio went on to allege: From 1910 to 1929, the United States erected dams in the Ohio River for navigational purposes. Since 1955, it has been replacing the earlier dams with higher ones. This has caused the waters of the river to rise and permanently inundate various areas of both Ohio and Kentucky. "As a result, the shores or banks of the Ohio River have been moved farther northerly and southerly as the water levels have increased by the damming of the river.” The north low water mark of 1792 “has been obscured by the increased elevation of the water levels.” Kentucky has claimed that the line between the two States is “along the present northerly shore line of the Ohio River rather than the 1792 northerly low water mark which is located to the south of the present north shore line.” Ohio “does now and has always claimed . . . that the boundary between it and Kentucky is the 1792 northerly low water mark.”
Leave to file the bill of complaint was granted. 384 U. S. 982 (1966). Kentucky by its answer admitted the allegations of the above-quoted numbered paragraphs of Ohio’s complaint. The Court then appointed the Honorable Phillip Forman as Special Master in the case. 385 U. S. 803 (1966).
Five years later, in August 1971, Ohio moved for leave to file an amended complaint. By this amendment Ohio would assert that the boundary between it and Kentucky is the middle of the Ohio River, or, only alternatively, is the 1792 low water mark on the northerly shore. We referred the motion to the Special Master. 404 U. S. 933 (1971). He held a hearing and in due course filed his report. 406 U. S. 915 (1972). The Master recommended that this Court enter its order denying Ohio’s petition for leave to amend. His conclusion rested on the ground “that the proposed amendment, in any view of its factual allegations, fails as a matter of law to state a cause of action.” Report 16. Upon the filing of Ohio’s exceptions and Kentucky’s reply, we set the matter for argument. 409 U. S. 974 (1972).
I
Accepted procedures for an ordinary case in this posture would probably lead us to conclude that the motion for leave to file should be granted, and the case would then proceed to trial or judgment on the pleadings. This, however, is not an ordinary case. It is one within the original and exclusive jurisdiction of the Court. Const., Art. Ill, §2; 28 U. S. C. § 1251 (a). Procedures governing the exercise of our original jurisdiction are not invariably governed by common-law precedent or by current rules of civil procedure. See United States Supreme Court Rule 9; Rhode Island v. Massachusetts, 14 Pet. 210 (1840). Under our rules, the requirement of a motion for leave to file a complaint, and the requirement of a brief in opposition, permit and enable us to dispose of matters at a preliminary stage. See, for example, Alabama v. Texas, 347 U. S. 272 (1954); California v. Washington, 358 U. S. 64 (1958); Virginia v. West Virginia, 234 U. S. 117, 121 (1914). Our object in original cases is to have the parties, as promptly as possible, reach and argue the merits of the controversy presented. To this end, where feasible, we dispose of issues that would only serve to delay adjudication on the merits and needlessly add to the expense that the litigants must bear.
This case is peculiarly susceptible to treatment of that kind. The allegations in Ohio’s proposed amendment are not as yet formally controverted by Kentucky. We, therefore, treat the new material as admitted. Kentucky asserts, however, that, even assuming the new allegations to be true, no cause of action is stated, for the subject matter of Ohio’s proposed amendment is barred as a matter of law.
I — I
In Handly s Lessee v. Anthony, 5 Wheat. 374 (1820), this Court stated that the boundary between Indiana and Kentucky was the low water mark on the western or northwestern side of the Ohio River. Handly was an action for ejectment brought by a plaintiff claiming under a grant from Kentucky against defendants claiming under a grant “from the United States, as being part of Indiana.” Id., at 375. The disputed land was a neck south of a channel, or bayou, that had formed north of the main river. When the river was high, the channel filled and cut off the land to the north. When the river was low, the channel was dry in part and the separation did not exist. The resolution of the case turned on whether the land was in Indiana or in Kentucky. Indiana, like Ohio, received its territory from the United States. The Court in Handly observed that the question “depends chiefly on the land, law of Virginia, and on the cession made by that State to the United States,” id., at 376, and concluded that the United States acquired title from Virginia when negotiations during the period from 1781-1784 resulted in Virginia’s ceding its lands north and west of the Ohio River to the Federal Government. Kentucky was received as a State of the Union in 1792 out of territory Virginia purported to retain at the time of the 1784 cession. The Court concluded, on the basis of this history, that Kentucky, through Virginia, extended up to the low water mark on the northern, or far, side of the Ohio River. Mr. Chief Justice Marshall enunciated the following, now familiar, principle:
“When a great river is the boundary between two nations or states, if the original property is in neither, and there be no convention respecting it, each holds to the middle of the stream. But when, as in this case, one State is the original proprietor, and grants the territory on one side only, it retains the river within its own domain, and the newly-created State extends to the river only. The river, however, is its boundary.” 5 Wheat., at 379.
The rule of the Handly case, as well as its specific application to the Kentucky-Indiana border, has been consistently adhered .to in subsequent decisions of this Court. Indiana v. Kentucky, 136 U. S. 479 (1890) (despite Indiana’s argument, id., at 486-493, that its boundary was the middle of the river); Henderson Bridge Co. v. Henderson City, 173 U. S. 592 (1899); Nicoulin v. O’Brien, 248 U. S. 113 (1918). It has been explicitly recognized by the Supreme Court of Ohio in Booth v. Shepherd, 8 Ohio St. 243, 247-248 (1858), where it was stated with far greater precision than the mere assumption the dissent suggests, post, at 654-655, that:
“The construction given to the Virginia deed of cession by the supreme court of the United States, having been thus acquiesced in and acted on by the courts, both of Virginia and Ohio, may be regarded as decisive of the question.”
See also Lessee of McCullock v. Aten, 2 Ohio 307, 310 (1826); Lessee of Blanchard v. Porter, 11 Ohio 138, 142 (1841). See Commonwealth v. Garner, 3 Gratt. 655 (Gen. Court of Va. 1846).
In order to counter this history, Ohio argues that, as it was not a party to the Handly case, or to any of the later cases in this Court that reaffirmed Handly, it is not bound by the rule there established, which it characterizes as dictum. In particular, Ohio contends that it is free to challenge the conclusion that Virginia, prior to ceding the land that now encompasses both Indiana and Ohio, held good title to that land.
Handly and the later decisions to which Ohio was not a party of course do not foreclose Ohio’s claim in a res judicata sense. But proceedings under this Court’s original jurisdiction are basically equitable in nature, Rhode Island v. Massachusetts, 14 Pet. 210 (1840), and a claim not technically precluded nonetheless may be foreclosed by acquiescence. Indiana v. Kentucky, 136 U. S., at 510, 518. We turn to that aspect of the present case.
Ill
By its amended complaint Ohio seeks to re-examine an accepted premise of the Handly decision and, in the process of doing so, to alter legal rights that, as a practical matter, have long been settled. By presently claiming ownership of half the Ohio River, Ohio does not assert that when Virginia ceded the lands northwest of the river, it intended to establish the river’s center as the line between Ohio and Kentucky, but, at the same time and thus inconsistently, to establish its northern edge as the line between Indiana and Kentucky. Rather, Ohio challenges the very postulate underlying the Handly decision, which must be taken, in practical effect, as establishing the entire northern boundary of Kentucky including its contact with Ohio. Ohio’s new theory is that Virginia did not have title to the lands north of the Ohio River in 1784 when Virginia surrendered its claim to the United States. Virginia’s claim, it is said, was baseless. Indeed, Ohio argues that title to these lands was hotly contested, with Virginia, New York, Massachusetts, Connecticut, and the United States all laying claim to the territory north of the river. The Continental Congress, fearing the threat this controversy posed for the youthful Nation, refused to resolve the disputed claims, and, instead, prevailed upon each of the claimants to forgo its claim in favor of the United States for the common good. Accordingly, Ohio contends, the premise of Handly — that Virginia had title to the northwest territory prior to ceding it to the United States, or, to say it another way, that it was the common proprietor of lands on both sides of the river — is historically invalid.
We need intimate no view on the merits of Ohio’s historical analysis, for the State’s long acquiescence in the location of its southern border at the northern edge of the Ohio River, and its persistent failure to assert a claim to the northern half of the river, convince us that it may not raise the middle-of-the-river issue at this very late date. The 1820 decision in Handly necessarily placed Ohio on notice that any claim it might assert to half the river would be precluded by the reasoning of that opinion. The Court in Handly concluded that the entire border between Indiana and Kentucky was the river’s northern edge. Virginia’s claim to the territory that is now Indiana arose from the same source as its claim to what is now Ohio. The lands to which Virginia purportedly surrendered title to the United States in 1784 encompassed both Ohio and Indiana. Ohio could not reasonably have believed, after Handly, that its claim over the northern half of the Ohio River rested on a footing different from that of Indiana.
Indeed, Ohio consistently has recognized that Handly and the cases that followed it foreclosed any claim that its border was located in the middle of the river. Even its original 1966 bill of complaint and supporting brief in this case so state. The decisions of Ohio’s highest court are to the same effect. And Ohio for over 150 years has failed to assert, through proceedings available in this Court, the claim it now would raise in the face of Kentucky’s legislative and judicial assertions of sovereignty over the river.
Ohio does not say that its failure to assert its claim over the past century and a half is due to any excusable neglect. The implications of Handly and later decisions of this Court are too clear to support that claim. Ohio recognized this in its initial brief here. Nor, in the light of the longstanding and unequivocal claims of Kentucky over the river, and Ohio’s failure to oppose those claims, may Ohio credibly suggest that it has not acquiesced. “The rule, long-settled and never doubted by this court, is that long acquiescence by one state in the possession of territory by another and in the exercise of sovereignty and dominion over it is conclusive of the latter’s title and rightful authority.” Michigan v. Wisconsin, 270 U. S. 295, 308 (1926). To like effect are Vermont v. New Hampshire, 289 U. S. 593, 613 (1933); Maryland v. West Virginia, 217 U. S. 1, 42-44 (1910); Louisiana v. Mississippi, 202 U. S. 1, 53-54 (1906); Virginia v. Tennessee, 148 U. S. 503, 523 (1893); Indiana v. Kentucky, 136 U. S., at 509-510, 518; Rhode Island v. Massachusetts, 4 How. 591, 639 (1846).
Here we have not only long acquiescence by Ohio in Kentucky’s open claims over the river, but also lines of cases by this Court and the courts of both Ohio and Kentucky that, for more than 150 years, placed Ohio on consistent notice of the inadequacy of the claim it now asserts. We find ourselves in agreement with the Special Master that Ohio is foreclosed from claiming that its boundary with Kentucky lies in the middle of the Ohio River.
The Special Master’s recommendation is adopted and Ohio’s motion for leave to amend its bill of complaint is denied. The case is remanded to the Special Master for further proceedings.
It is so ordered.
1792 is the year Kentucky became a State. 1 Stat. 189.
Recommendation of the Continental Congress, September 6, 1780, 10 W. Hening, Laws of Virginia 562 (1822); Resolution of the General Assembly of Virginia, January 2, 1781, conditioned, among other things, upon ratification of the Articles of Confederation and upon like cessions by other States, id., at 564, 567; Act of the Continental Congress, September 13, 1783, 25 J. of the Cont. Cong. 1774-1789, p. 559 (1922); Act of Confirmation, October 20, 1783, 11 W. Hening, Laws of Virginia 326 (1823); Act of the Continental Congress, March 1, 1784, 1 Laws of the United States 472 (B. & D. ed. 1815).
The 1781 Virginia resolution recited that the Commonwealth “will yield to the congress of the United States ... all right, title, and claim that the said commonwealth hath to the lands northwest of the river Ohio.” 10 W. Hening, Laws of Virginia 564 (1822). Among the proposed conditions was also a guarantee by the United States to Virginia of “all the remaining territory of Virginia included between the Atlantic Ocean and the south east side of the river Ohio.” Id., at 566. This latter condition was not agreed to by the Congress by its Act of 1783. 25 J. of the Cont. Cong. 1774-1789, p. 563 (1922).
The 1783 Act referred to territory “to the north-west of the river Ohio.” 11 W. Hening, Laws of Virginia 327. So, too, did the deed of March 1, 1784, from Virginia to the United States accepted by Congress on the same day. 1 Laws of the United States, supra, at 474.
“Upon this question of boundary nothing can be added to what was said in the eases cited; and it must be assumed as indisputable that the boundary of Kentucky extends to low-water mark on the western and northwestern banks of the Ohio River.” Henderson Bridge Co. v. Henderson City, 173 U. S. 592, 613 (1899).
There is a possible intimation to the contrary in the bridge tax case of Covington á Cincinnati Bridge Co. v. Mayer, 31 Ohio St. 317, 327, 329 (1877). The case appears, however, to have been resolved on the content of the bridge company’s Ohio charter granting permission for the erection of the bridge. See Sebastian v. Covington & Cincinnati Bridge Co., 21 Ohio St. 451 (1871).
See Indiana v. Kentucky, 136 U. S. 479, 505 (1890). See also the deed of March 1, 1784, referred to in n. 2, supra, from Virginia to the United States. On August 7, 1789, Congress passed “An Act to provide for the Government of the Territory Northwest of the river Ohio.” 1 Stat. 50. In 1800, this territory was divided into two separate governments. 2 Stat. 58. And on April 30, 1802, the enabling Act for the admission of Ohio was passed. 2 Stat. 173. The State was formed out of the eastern half of the theretofore divided territory and was “bounded ... on the south by the Ohio river,” ibid.; the land in the eastern division not included within the boundaries described for Ohio “is hereby attached to, and made a part of the Indiana territory.” Id., at 174.
“The State of Ohio does now, and has always claimed and maintained that the boundary between it and the State of Kentucky is the northerly low water mark of the Ohio River, as that mark existed in the year 1792 when Kentucky became a state.” Brief in support of motion for leave to file complaint 8. (Emphasis in original.)
In 1810, a decade before the Handly decision, the Kentucky Legislature enacted the following statute:
“Sec. 1 Be it enacted by the General Assembly, That each county of this commonwealth, calling for the river Ohio, as the boundary line, shall be considered as bounded in that particular by the state line on the north west side of said river, and the bed of the river and the islands, therefore shall be within the respective counties, holding the main land opposite thereto, within this state, and the several county tribunals, shall hold jurisdiction accordingly.” Acts of Kentucky, 1809, p. 100 (1810); 1 Statute Laws of Kentucky 268 (1834).
See also 2 Ky. Rev. Stat., Tit. 1, c. 1, p. 2 (1971).
Commonwealth v. Henderson County, 371 S. W. 2d 27, 29-30 (1963); Louisville Sand & Gravel Co. v. Ralston, 266 S. W. 2d 119, 121-122 (1954); Shannon v. Streckfus Steamers, Inc., 279 Ky. 649, 653, 131 S. W. 2d 833, 835 (1939); McFarland v. McKnight, 45 Ky. 500, 510 (1846); Church v. Chambers, 3 Dana 274, 278-279 (Ct. App. Ky. 1835); Fleming v. Kenney, 27 Ky. 155, 158 (1830); McFall v. Commonwealth, 2 Metc. 394, 396 (Ky. 1859).
“Like Ohio, the State of Indiana was formed from the land ceded by Virginia; therefore, it has for its southern boundary the Ohio River. See 3 Stat. 289 (1816), and 3 Stat. 399 (1816). Thus, a determination of the boundary between the states of Indiana and Kentucky would control the determination of the boundary between the states of Ohio and Kentucky.” Brief in support of motion for leave to file complaint 10.
The situation, of course, is otherwise when the States’ boundary dispute has been open, continuous and of long standing. See, for example, New Jersey v. Delaware, 291 U. S. 361, 376-377 (1934); Oklahoma v. Texas, 272 U. S. 21, 46-47 (1926); Arkansas v. Tennessee, 246 U. S. 158, 172 (1918).