Contiguous United States
The contiguous United States refers to the 48 adjoining U.S. states on the continent of North America that are south of Canada and north of Mexico, plus the District of Columbia. The term excludes the states of Alaska and Hawaii, and all off-shore U.S. territories and possessions, such as Puerto Rico.
Together, the 48 contiguous states and D.C. occupy a combined area of 3,119,884.69 square miles (8,080,464.3 km2), which is 1.58% of the total surface area of the Earth. Of this, 2,959,064.44 square miles (7,663,941.7 km2) is land, composing 83.65% of U.S. land area. Officially, 160,820.25 square miles (416,522.5 km2) is water area, composing 62.66% of the nation's water area. The 2010 census population was 306,675,006, composing 99.33% of the nation's population, and a density of 103.639 inhabitants/sq mi (40.015/km²), compared to 87.264/sq mi (33.692/km²) for the nation as a whole.
Other terms 
While coterminous U.S. has the precise meaning of contiguous U.S. (both adjectives meaning "sharing a common boundary"), other terms commonly used to describe the 48 contiguous states have a greater degree of ambiguity.
Continental United States 
Because Alaska is also on the North American continent, the term continental United States, if interpreted literally, would also include that state, so the term is sometimes qualified with the explicit inclusion or exclusion of Alaska to resolve any ambiguity. 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. However, even before Alaska became a state, it was sometimes included within the "Continental US".
CONUS and OCONUS 
CONUS, a technical term used by the U.S. Department of Defense, General Services Administration, NOAA/National Weather Service, and others has been defined both as the continental United States, and as the 48 contiguous states. The District of Columbia is not always specifically mentioned as being part of CONUS.
The Lower 48 
The term Lower 48 may or may not include the District of Columbia (D.C.), which is not part of any of the 48 states. However common usage is that it includes D.C. and simply means the contiguous US as a region, as there is no typical need to politically separate D.C. from the region in everyday speech. Lower 48 is also ambiguously misleading, since all the major islands of Hawaii are farther south than the most southern point of any other state, and thus Hawaii could be considered "lower" than any other 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. Otherwise it is avoided as a misnomer.
Terms used in the non-contiguous states 
Both Alaska and Hawaii have their own unique labels for the contiguous United States because of their own locations relative to them.
Alaska became the 49th (and northernmost) 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 the Canadian province of British Columbia. 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. The term Lower 48 was for many years, and still is, the most common Alaskan equivalent for "contiguous United States".
Hawaii became the 50th state of the United States on August 21, 1959. It is the southernmost and, so far, the latest state to join the Union. Not part of any continent, Hawaii is located in the Pacific Ocean, about 2,200 miles (3,500 km) from North America and almost halfway to Asia. In Hawaii and overseas American territories, for instance, the terms the Mainland or U.S. Mainland are often used to refer to the continental United States.
Non-contiguous areas within the contiguous United States 
Some parts of the contiguous United States are accessible by road only by travelling on Canadian soil. Point Roberts, Washington; Elm Point, Minnesota; and the Northwest Angle in Minnesota are three such places. Alburgh, Vermont is not directly connected by land, but is accessible by road via bridges from New York and Vermont.
See also 
- "United Airlines website". Retrieved 2012-04-04. "Contiguous United States: The 48 adjoining states and the District of Columbia."
- Random House (1991). Random House Webster's College Dictionary. New York: Random House. ISBN 0-679-40110-5.
- These maps show the contiguous 48 states and D.C., but not Alaska and Hawaii.
- "Military Bases in the Contiguous United States". National Park Service, U.S. Department of the Interior. Retrieved 2012-11-28.
- "Soil Moisture Regimes of the Contiguous United States". U.S. Department of Agriculture. Retrieved 2012-11-28.
- "Resident Population Data - 2010 Census". United States Census Bureau. Retrieved 2011-01-30.
- "National Geographic Style Manual". Retrieved 2012-04-04. "The continental United States comprises the 48 contiguous, or coterminous, states plus Alaska."
- "United Cargo website". Retrieved 2012-04-04. "Continental United States: The 48 adjoining states, Alaska and District of Columbia."
- "Alaska Airlines website". Retrieved 2012-04-04. "The Continental U.S. includes the lower 48 states as well as the State of Alaska, unless otherwise specified."
- Inland Marine and Transportation Insurance. 1949 <before statehood>. Retrieved 2012-04-04. "In the absence of any such statement, Alaska probably would be regarded as a part of the continental United States."
- "U.S. Navy Style Guide". Retrieved 2012-04-04. "CONUS - "Continental United States" CONUS refers to the 48 contiguous states."
- Internal Revenue Code. 2007. "the term "United States mainland" means the continental United States (not including Alaska)."
- United States Code Annotated. 1927. "Such subsection is further amended by striking out "continental United States (including Alaska)" ...'"
- "... for the states and territories Outside of the Continental United States. (Includes Alaska, ...) ..." National Voluntary Organizations Active in Disaster[dead link]
- "... outside the continental United States (includes Alaska and Hawaii, as well as Canada and all foreign countries)... "Equimax candidate listing". Archived from the original on 2011-07-10. Retrieved 2012-11-28.
- "Abstract of the 1900 Census (1904), p.xiii" (PDF). "The area ... is continental United States, by which is meant that part of the United States lying on the continent of North America south of the Canadian boundary. It thus excludes Alaska and the recent insular accessions of Hawaii, Porto Rico (sic), the Philippine Islands, Guam, Samoa..."
- "... merchandise to foreign countries from continental United states, Puerto Rico, and the territories of Alaska and Hawaii." United States Foreign Trade (1950-1953)
- "In the absence of any such statement, Alaska probably would be regarded as a part of the continental United States." Inland Marine and Transportation Insurance (1949)
- "Per Diem Rates (CONUS and OCONUS)". United States General Services Administration.
- "U.S. Navy Style Guide". "CONUS - "Continental United States." CONUS refers to the 48 contiguous states. It is not synonymous with United States. CONUS is acceptable on first reference." "CONUS" seems to be used primarily by the American military and the Federal government and those doing business with them.
- "Glossary of Army Terms". Retrieved 2012-04-04. ""OCONUS: Outside Continental United States"
- "National Geographic Style Manual". Retrieved 2012-04-04. "Use contiguous, or conterminous, for the 48 states. The continental United States comprises the 48 contiguous, or conterminous, states plus Alaska."
- Speak Alaskan
- About Alaska
- Ross, Oakland (3 June 2011). "Orphans of the atlas". Toronto Star. Retrieved 2011-06-05.