| 36th | Top regions of the United States |
The term contiguous United States refers to the 48 U.S. states located on the North American continent south of the U.S. border with Canada, plus the District of Columbia.[1] The term excludes the states of Alaska and Hawaii, and all off-shore U.S. territories and possessions, such as Puerto Rico.[2][3][4][5]
Together, the 48 contiguous states and D.C. have an area of 3,119,884.69 square miles (8,080,464.25 km²). Of this, 2,959,064.44 sq mi (7,663,941.71 km²) is land, comprising 83.65% of U.S. land area. Officially, 160,820.25 sq mi (416,522.38 km²) is water area, comprising 62.66% of the nation's water area. Its 2000 census population was 279,583,437, comprising 99.35% of the nation's population. Its population density was 94.484 inhabitants/sq mi (36.480/km²), compared to 79.555/sq mi (30.716/km²) for the nation as a whole.[6]
The map below shows the contiguous United States and, in an inset box in the lower left, the two states that are not contiguous.

While coterminous U.S. and conterminous U.S. have the same precise meaning as contiguous U.S., other terms commonly used to describe the 48 contiguous states have some degree of ambiguity.
Because Alaska is also on the North American continent, the term continental United States, if interpreted literally, should also include that state,[7] so the term is sometimes qualified with the explicit inclusion or exclusion of Alaska to resolve any ambiguity.[8][9][3][10][11] The term was in use prior to the admission of Alaska and Hawaii as states of the United States, and at that time usually excluded outlying territories of the U.S.[12][13] However, even before Alaska became a state, it was sometimes included within the "Continental US".[14]
The term lower 48 may or may not include the District of Columbia (which is not part of any of the 48 states), and may or may not exclude Hawaii (which is the southern-most U.S. state). The National Geographic style guide recommends the use of contiguous or conterminous United States instead of "lower 48" when the 48 states are meant, unless used in the context of Alaska.[15]
CONUS is a technical term used by the US Department of Defense which is specifically defined as the 48 contiguous states but is silent on the District of Columbia.[5] OCONUS is the same term with addition of O for outside, thus Outside of Contiguous United States (OCONUS).
Both Alaska and Hawaii, because of their own location relative to the contiguous United States, have their own unique labels for it.
Alaska became the 49th state of the United States on January 3, 1959. Alaska is on the northwest end of the North American continent, but separated from the rest of the United States by Canada. In Alaska, given the ambiguity surrounding the usage of continental, the term "continental United States" is almost unheard of when referring to the contiguous 48 states. Several other terms have been used over the years. Most Americans are familiar with the term "Lower 48", which for many years was the most common Alaskan equivalent for "contiguous United States". However, since the 1980s Alaskans have increasingly adopted the term Outside to refer to the rest of the United States. Alaskans will speak of going Outside to vacation or will refer to being born Outside.[16][17][18]
Hawaii became the 50th state of the United States on August 21, 1959. The Hawaiian Islands are located in Oceania and are about 2,200 miles (3,500 km) from the North American mainland. In Hawaii and overseas American territories, for instance, the terms "the Mainland" or "U.S. Mainland" are used to refer to the continental United States.
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