Territorial evolution of the United States
In the Lee Resolution, passed by the Second Continental Congress two days prior, the colonies resolved that they were free and independent states.
Their independence was recognized by Great Britain in the Treaty of Paris of 1783, which concluded the American Revolutionary War.
This effectively doubled the size of the colonies, now able to stretch west past the Proclamation Line to the Mississippi River.
This land was organized into territories and then states, though there remained some conflict with the sea-to-sea grants claimed by some of the original colonies.
The cultural endeavor and pursuit of manifest destiny provided a strong impetus for westward expansion in the 19th century.
[6] Puerto Rico and Guam remain territories, and the Philippines became independent in 1946, after being a major theater of World War II.
Four states (Louisiana, Missouri, Nevada, and Pennsylvania) have expanded substantially by acquiring additional federal territory after their initial admission to the Union.
[25][26] Many states had vaguely defined and surveyed borders; these are not noted as contested in the maps unless there was an active dispute.
In 1816, construction began on an unnamed fort nicknamed "Fort Blunder" on a peninsula in Lake Champlain that, while south of the surveyed border, was discovered to be north of 45° north, which was the border set by the Treaty of Paris and thus in British territory.
[297] On this same date several islands, Cagayan de Sulu and Sibutu among them, were purchased from Spain and assigned to the Philippines, which was then being governed as a U.S. insular area.
[361][437] 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.
[459] The sudden changes often created bancos (land surrounded by bends in the river that became segregated from either country by a cutoff, often due to rapid accretion or avulsion of the alluvial channel), especially in the Lower Rio Grande Valley.
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.
[460] In all cases of these adjustments along the Rio Grande under the 1905 convention, which occurred on 37 different dates from 1910 to 1976, the transferred land was minuscule (ranging from one to 646 acres) and uninhabited.
