Territorial evolution of the United States

The United States of America was created on March 1, 1781, with the entry into force of the Articles of Confederation. In its history, it has gained independence from Great Britain, replaced its government with a new constitution, endured a civil war, and expanded across North America and the seas, growing from thirteen states to fifty states and many territories from the western Pacific Ocean to the Caribbean Sea.

Table of changes

 * Key to map colors
 * {{legend|#CD5C5C|disputed area of United States}}
 * {{legend|#FFFFE0|undisputed area of United States (outline view in maps of international disputes; internal view in domestic maps)}}
 * {{legend|#FFDEAD|United States territories (domestic maps)}}
 * {{legend|#c0c09c|area changed by event}}


 * Click on any map to view a larger version in Wikimedia Commons. Click on that Commons map to further enlarge map details.

Bancos along the Rio Grande
The Banco Convention of 1905 between the United States and Mexico allowed, in the event of sudden changes in the course of the Rio Grande (as by flooding), for the border to be altered to follow the new course. The sudden changes often created bancos, land left behind when curves in the river are cut off by rapid erosion of the channel or are intentionally cut to re-align it. When these bancos are created, the International Boundary and Water Commission investigates if land previously belonging to the United States or Mexico is to be considered on the other side of the border. In all cases of these adjustments under the 1905 convention, which occurred on 37 different dates from 1910 to 1976, the transferred land was minuscule (ranging in size from 1 acre to 646 acres) and uninhabited. Indeed, some of the early bancos that were exchanged (including several created by floods in the mid-19th century) sustained further boundary adjustments from later avulsive changes and river straightening projects. Due to this fact and the small sizes of ceded land, these changes are not listed here; please see the articles linked above for more detail. This information is also available as a kmz file mapped at this location.