Contiguous United States: Geography, Terminology, and Key Facts

When discussing the geography of North America, the term contiguous United States refers to the 48 adjoining states and the District of Columbia. Also known as the conterminous United States, this region forms the central landmass of the country. While often used interchangeably with "the mainland," the specific terminology used can change depending on whether you are speaking to a resident of Alaska, Hawaii, or a U.S. territory.

A map showing the contiguous United States

Defining the Boundaries

The contiguous United States is defined by its shared boundaries. This grouping specifically excludes the two non-contiguous states—Alaska and Hawaii—as well as various offshore insular areas. These territories include American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the U.S. Virgin Islands.

It is important to distinguish between several frequently confused terms:

Contiguous/Conterminous United States: The 48 adjoining states and the District of Columbia.
Continental United States: A broader term that includes the 48 contiguous states plus Alaska, as Alaska is part of the North American continent.
Mainland United States: Technically refers to parts of states connected to the North American landmass, which may exclude certain islands like the Aleutian Islands or the Florida Keys.
CONUS: A technical acronym used by the Department of Defense and other agencies to refer to the continental United States or the 48 contiguous states.

Map highlighting Alaska and Hawaii's geographical relationship to the contiguous United States. Alaska, in red, is in the upper part of the map, while Hawaii is the islands also in red to the far left. Contiguous US is near the center in white

Geography and Scale

The contiguous United States covers a massive expanse of 3,119,884.69 square miles. Of this total, approximately 2,959,064.44 square miles is actual land, making up 83.65 percent of the nation's total land area. This landmass is comparable in size to the continent of Australia. The remaining area consists of 160,820.25 square miles of water.

In terms of distance, the greatest north-south line measures 1,650 miles (2,660 km). The longest distance achievable on a great-circle route (the shortest distance between two points on a sphere) entirely within the contiguous U.S. is 2,802 miles (4,509 km), stretching from Florida to Washington state.

Geographic Overview of the Contiguous United States
Category	Measurement (Imperial)	Measurement (Metric)
Total Area	3,119,884.69 sq mi	8,080,464.3 km²
Land Area	2,959,064.44 sq mi	7,663,941.7 km²
Water Area	160,820.25 sq mi	416,522.5 km²
Max Coast-to-Coast Distance	2,802 miles	4,509 km
Max North-South Distance	1,650 miles	2,660 km

Population and Global Standing

According to the 2020 U.S. Census, the contiguous United States had a population of 328,571,074. This represents 99.13 percent of the entire nation's population. The population density in this region is 111.04 inhabitants per square mile, which is higher than the national average of 93.844 inhabitants per square mile.

If the contiguous United States were considered an independent country, it would rank fifth in the world by area, following Russia, Canada, China, and Brazil. However, when including Alaska, Hawaii, and overseas territories, the total United States ranks third or fourth globally.

Regional Perspectives and Local Terms

Terminology often shifts based on the perspective of the speaker. For example, residents of non-contiguous areas use specific labels to describe the 48 states:

Alaska

Alaska became the 49th state on January 3, 1959. Because it is separated from the rest of the U.S. by British Columbia, Canada, many Alaskans refer to the contiguous states as the Lower 48 or simply "the Outside."

Hawaii

As the 50th state, admitted on August 21, 1959, Hawaii is located in the Pacific Ocean, roughly 2,200 miles from North America. In Hawaii, the 48 states are commonly referred to as the Mainland.

U.S. Territories

In territories such as Puerto Rico and the U.S. Virgin Islands, the term stateside is frequently used to refer to the mainland United States. In American Samoa, the contiguous U.S. is often called "the states" or the "mainland United States."

Key Facts

The contiguous U.S. consists of 48 adjoining states and the District of Columbia.
It accounts for 99.13% of the total U.S. population as of the 2020 Census.
The term conterminous is a precise synonym for contiguous.
The continental United States includes Alaska, whereas the contiguous U.S. does not.
The largest coast-to-coast distance within the contiguous U.S. is 2,802 miles.

Frequently Asked Questions

What is the difference between contiguous and continental United States?

The contiguous United States refers only to the 48 states that share a border. The continental United States includes those 48 states plus Alaska, because Alaska is part of the North American continent.

What does the term "Lower 48" mean?

"Lower 48" is a colloquial term used to describe the 48 contiguous states, most commonly used in the context of Alaska to distinguish the mainland from the state.

Is the District of Columbia part of the contiguous United States?

Yes, the District of Columbia is included within the contiguous United States.

What is OCONUS?

OCONUS stands for "Outside of Continental United States" and is a technical term used by various government and military organizations.

Are there parts of the contiguous U.S. that require driving through Canada?

Yes, certain areas such as Point Roberts, Washington, and the Northwest Angle in Minnesota are non-contiguous portions of the U.S. that can only be reached by road through Canada.