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TREATY OF 1884. The role of the Rio Grande as an international boundary was a subject of dispute during the Mexican War after Texas was annexed by the United States in 1845. The Treaty of Guadalupe Hidalgo, which ended the war in 1848, provided that the boundary line between the two countries would follow the middle or deepest channel of the Rio Grande. The treaty, however, failed to end the controversy. Seasonal fluctuations in the volume of water carried by the Rio Grande caused erosion of the riverbanks as well as sudden changes in the channel. Major flooding could produce, destroy, or modify islands. Under international practice, if gradual changes occurred in riverbanks through erosion or accretion, then the boundary would follow the new river channel. In the event of a sudden change, however, the boundary would not change but would run along the line of the old riverbed. A joint survey by the United States and Mexico in the 1850s had assigned the various islands in the Rio Grande to one or the other country. Islands north of the main channel belonged to the United States, and those south of it were under Mexican jurisdiction. Although the United States and Mexico agreed on these general principles, the two countries had never signed a formal treaty incorporating them and often encountered problems in trying to apply the principles to specific cases. Complicating the issue was the fact that the islands in the Rio Grande were often centers for illegal activities, especially smuggling and rustling. In 1874 and 1875 the Mexican government presented two draft treaties urging the United States to reach an agreement to deal with these problems. Although the two treaties incorporated principles already accepted by the United States, no response was made until 1884, when a dispute developed over the island of Morteritos, near Roma, Texas, on the Rio Grande. In January officials from Roma occupied the island. Mexican authorities protested the "invasion" and claimed that the island was part of the Mexican state of Tamaulipas; they agreed to allow the status quo on the island pending negotiations.

Mexico's claim to the island was based on a survey made in April 1880 by one of its engineers, Ignacio Garfias. The Garfias report indicated that the deepest channel of the river was north of the island and always had been, and that Morteritos was therefore Mexican territory. Mexico also pointed out that the United States had never occupied the island, nor had it interfered with Mexican authorities on the island prior to 1884. The United States government's response was that Mexican officials had simply misread the map drawn up by the Emory Boundary Commission survey team in the 1850s (see EMORY, WILLIAM HEMSLEY). The Mexican government had confused the island of Sabinitos, acknowledged by the United States to belong to Mexico, with the island of Morteritos. In 1884 Mexico admitted that there had been confusion over the islands in question and recognized American jurisdiction over Morteritos in exchange for a formal treaty dealing with the question of changes in the Rio Grande. Once the specific issue of Morteritos had been settled, negotiations for a treaty went forward rapidly. In November 1884 the United States and Mexico signed a boundary treaty to "avoid difficulties which may arise through changes of [river] channel." The treaty recognized principles that both countries had been operating on from the beginning. Under the agreement gradual changes in the Rio Grande through erosion or accretion would lead to a change in the boundary, which would follow the new channel. Sudden changes in the course of the river would not lead to a change in the boundary; the boundary would continue to lie along the original riverbed as set down by the Treaty of Guadalupe-Hidalgo and the boundary survey of the 1850s. The Treaty of 1884 established general principles for dealing with boundary problems arising from changes in the river. An additional boundary convention signed in 1889 set up an International Boundary Commission (see INTERNATIONAL BOUNDARY AND WATER COMMISSION) to process all disputes arising out of changes in the river. The Treaty of 1884 was the basis for resolving a number of disagreements in the twentieth century, including the lengthy Chamizal dispute at El Paso.


Don M. Coerver, "From Morteritos to Chamizal: The U.S. Mexican Boundary Treaty of 1884," Red River Valley Historical Review 2 (Winter 1975). William M. Malloy, comp., Treaties, Conventions, International Acts, Protocols and Agreements between the United States of America and Other Powers, 1776–1909 (2 vols., Washington: GPO, 1910).

Don M. Coerver


The following, adapted from the Chicago Manual of Style, 15th edition, is the preferred citation for this article.

Don M. Coerver, "TREATY OF 1884," Handbook of Texas Online (, accessed April 20, 2014. Uploaded on June 15, 2010. Published by the Texas State Historical Association.