Contiguous United States

Contiguous United States
Usa_edcp_location_map.svg: Uwe Dedering derivative work: –droll [chat] · CC BY-SA 3.0 · source
Name	Contiguous United States
Capital	Washington, D.C.
Largest city	New York City
Official languages	English language
Area km2	8,080,464
Population	331,449,281 (2020 census)
Population density km2	36.7
Currency	United States dollar
Time zone	Multiple time zones
Legislature	United States Congress
Established event1	United States Declaration of Independence
Established date1	July 4, 1776

Contents

Contiguous United States is the region of the United States consisting of the 48 adjoining states on the North American continent and the District of Columbia. It excludes the noncontiguous states of Alaska and Hawaii as well as overseas territories such as Puerto Rico, Guam, and American Samoa. The area contains major population centers including New York City, Los Angeles, Chicago, and Houston and serves as the core of federated institutions such as the United States Congress and federal agencies like the Federal Reserve System.

Definition and Terminology

The commonly used term refers to the 48 adjoining states and District of Columbia, distinguished from Alaska and Hawaii by contiguity. Variants of the term appear in legal and cartographic contexts such as the United States Census Bureau definitions, the Office of Management and Budget statistical areas, and Supreme Court cases like Worcester v. Georgia that shaped federal jurisdiction. Related phrases include “lower 48,” used in United States Geological Survey maps, and “continental United States,” a term with differing usage in Department of Defense documents and United States Postal Service routing.

The region spans from the Atlantic coast of Maine and Massachusetts to the Pacific coast of California and Oregon, and from the border with Canada along provinces such as Ontario and Quebec to the border with Mexico adjacent to states like Texas and California. Major physiographic provinces include the Appalachian Mountains, the Great Plains, the Rocky Mountains, and the Sierra Nevada. Major rivers such as the Mississippi River, Missouri River, Colorado River, and Rio Grande define drainage basins and interstate boundaries, while the Great Lakes—including Lake Superior and Lake Michigan—form an international border with Canada. Coastal zones include the Gulf of Mexico and the Atlantic Ocean, with strategic ports at New Orleans, Baltimore, Seattle, and Los Angeles.

European colonization brought competing claims by powers such as Spain, France, and Great Britain, resulting in events like the French and Indian War and treaties including the Treaty of Paris (1783). Expansionist policies manifested in acquisitions such as the Louisiana Purchase, the Annexation of Texas, and the Mexican–American War, which produced the Treaty of Guadalupe Hidalgo. The constitutional framework evolved through the United States Constitution and amendments ratified after debates in the Federalist Papers era and conflicts including the American Civil War. Political developments include the emergence of parties like the Democratic Party and Republican Party, landmark legislation such as the Homestead Act, and progressive reforms associated with figures like Theodore Roosevelt and Franklin D. Roosevelt.

The population is diverse, shaped by migration waves from regions such as Ireland, Italy, Germany, China, and Mexico, and by movements like the Great Migration and post‑World War II suburbanization tied to the Interstate Highway System. Urban agglomerations include the Northeast megalopolis, Los Angeles metropolitan area, and Chicago metropolitan area, while economic power centers encompass Wall Street, Silicon Valley, Houston energy sector, and the Rust Belt. Sectors range from finance, exemplified by New York Stock Exchange and Federal Reserve Bank of New York, to technology leaders like Apple Inc., Microsoft, and Google, to agriculture in the Midwest and energy production in Texas and North Dakota via fields like Permian Basin. Social policy debates have involved landmark statutes such as the Civil Rights Act of 1964 and programs initiated under the New Deal.

An extensive network includes the Interstate Highway System, major rail corridors like those operated by Union Pacific Railroad and BNSF Railway, and aviation hubs such as Hartsfield–Jackson Atlanta International Airport, Los Angeles International Airport, and Chicago O'Hare International Airport. Inland waterways utilize the Mississippi River system and the Erie Canal historically, while seaports include Port of New York and New Jersey and Port of Los Angeles. Energy infrastructure comprises interstate pipelines, nuclear plants regulated by the Nuclear Regulatory Commission, and grid operators such as PJM Interconnection. Telecommunications and broadband initiatives engage firms like AT&T and Verizon Communications.

Climatic regimes range from humid continental in Minnesota and Maine to Mediterranean in California and subtropical in Florida and the Gulf Coast, with semi‑arid and arid zones in the Great Basin and Southwest. Environmental issues include air quality concerns in metropolitan areas like Los Angeles and Phoenix, water resource disputes exemplified by the Colorado River Compact, and conservation efforts in federal and state parks such as Yellowstone National Park and Yosemite National Park. Biodiversity hotspots include the Everglades National Park and Pacific coastal ecosystems, while climate policy intersects with international accords such as the Paris Agreement and domestic statutes influenced by litigation in courts like the Supreme Court of the United States.