The territory of the United States and its overseas possessions has evolved over time, from the colonial era to the present day. It includes formally organized territories, proposed and failed states, unrecognized breakaway states, international and interstate purchases, cessions, and land grants, and historical military departments and administrative districts. The last section lists informal regions from American vernacular geography known by popular nicknames and linked by geographical, cultural, or economic similarities, some of which are still in use today.
For a more complete list of regions and subdivisions of the United States used in modern times, see List of regions of the United States.
† - indicates failed legal entities
Unlike the land to the east, most of the land west of the Mississippi River was under French or Spanish rule until the first years of the 19th century.
The following are state cessions made during the building of the U.S.
The following is a list of the 31 U.S. territories that have become states, in the order of the date organized (all were considered incorporated):
The following are land grants, cessions, defined districts (official or otherwise) or named settlements made within an area that was already part of a U.S. state or territory that did not involve international treaties or Native American cessions or land purchases.
These entities were sometimes the only governmental authority in the listed areas, although they often co-existed with civil governments in scarcely populated states and territories. Civilian administered "military" tracts, districts, departments, etc., will be listed elsewhere.
During the American Civil War, the Department of the Pacific had six subordinate military districts:
The Department of California (1858–1861) comprised the southern part of the Department of the Pacific: California, Nevada, and southern part of Oregon Territory; merged into the Department of the Pacific as the District of California.
The Department of Oregon (1858–1861) comprised the northern part of the Department of the Pacific: Washington Territory and Oregon Territory.
These "territories" had actual, functioning governments (recognized or not):
These are functioning governments created as a result of the attempted secession of the Confederacy during the American Civil War (1861–1865). Some were enclaves within enemy-held territories:
These were regions disassociated from neighboring areas due to opposing views:
Belts are loosely defined sub-regions found throughout the United States that are named for a perceived commonality among the included areas, which is often related to the region's economy or climate.