The United States of America (USA), commonly referred to as the United States (US), America, or simply the States, is a federal republic consisting of 50 states, 16 territories, a federal district, and various overseas extraterritorial jurisdictions. The 48 contiguous states and the federal district of Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and nine unpopulated territories in the Pacific and the Caribbean. At 3.79 million square miles (9.83 million km2) in total and with around 316 million people, the United States is the fourth-largest country by total area and third largest by population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife.
Paleo-indians migrated from Asia to what is now the US mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located along the Atlantic seaboard. Disputes between Great Britain and these colonies led to the American Revolution. On July 4, 1776, delegates from the 13 colonies unanimously issued the Declaration of Independence. The ensuing war ended in 1783 with the recognition of independence of the United States from the Kingdom of Great Britain, and was the first successful war of independence against a European colonial empire. The current Constitution was adopted on September 17, 1787. The first 10 amendments, collectively named the Bill of Rights, were ratified in 1791 and guarantee many fundamental civil rights and freedoms.
The Gulf of Mexico (Spanish: Golfo de México) is an ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In Texas and Louisiana it is often called the "Third Coast," in comparison with the U.S. Atlantic and Pacific coasts. The shape of its basin is roughly oval and is approximately 810 nautical miles (1,500 km) wide and filled with sedimentary rocks and debris. It is connected to the Atlantic Ocean through the Florida Straits between the U.S. and Cuba, and with the Caribbean Sea (with which it forms the American Mediterranean Sea) via the Yucatan Channel between Mexico and Cuba. With this narrow connection to the Atlantic, the Gulf experiences very small tidal ranges. The size of the Gulf basin is approximately 615,000 mi² (1.6 million km²). Almost half of the basin is shallow continental shelf waters. At its deepest it is 14,383 ft (4,384 m) at the Sigsbee Deep, an irregular trough more than 300 nautical miles (560 km) (550 km) long. The basin contains a volume of roughly 660 quadrillion gallons (2.5 × 106 km3). It was formed approximately 300 million years ago as a result of plate tectonics.
The Central Mexican Plateau, also known as the Mexican Altiplano (Spanish: Altiplanicie Mexicana), is a large arid-to-semiarid plateau that occupies much of northern and central Mexico. Averaging 1,825 m (5,988 ft) above sea level, it extends from the United States border in the north to the Trans-Mexican Volcanic Belt in the south, and is bounded by the Sierra Madre Occidental and Sierra Madre Oriental to the west and east, respectively.
A low east-west mountain range in the state of Zacatecas divides the plateau into northern and southern sections. These two sections, called the Northern Plateau (Spanish: Mesa del Norte) and Central Plateau (Spanish: Mesa Central), are now generally regarded by geographers as sections of one plateau.
The Mexico–United States border is an international border running from Imperial Beach, California, and Tijuana, Baja California, in the west to Matamoros, Tamaulipas, and Brownsville, Texas, in the east. The border, separating Mexico and the United States from each other, traverses a variety of terrains, ranging from major urban areas to inhospitable deserts. From the Gulf of Mexico, it follows the course of the Rio Grande (Río Bravo del Norte) to the border crossing at El Paso, Texas, and Ciudad Juárez, Chihuahua; westward from that binational conurbation it crosses vast tracts of the Sonoran and Chihuahuan Desert, the Colorado River Delta, westward to the binational conurbation of San Diego and Tijuana before reaching the Pacific Ocean.
The border's total length is 3,145 km (1,954 mi), according to figures given by the International Boundary and Water Commission. It is the most frequently crossed international border in the world, with approximately 350 million people legally crossing per year.
The Rio Grande (/ /; Spanish: Río Bravo del Norte or Río Bravo, [ˈri.o ˈβra.βo]) is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico–United States border. According to the International Boundary and Water Commission, its total length was 1,896 miles (3,051 km) in the late 1980s, though course shifts occasionally result in length changes. Depending on how it is measured, the Rio Grande is the fourth or fifth longest river system in North America.
The river serves as a natural border between the U.S. state of Texas and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. A very short stretch of the river serves as the boundary between the U.S. states of Texas and New Mexico. Since the mid–20th century, heavy water consumption of farms and cities along the river has left only 20% of its natural discharge to flow to the Gulf. Near the river's mouth, the heavily irrigated Rio Grande Valley is an important agricultural region. The Rio Grande is one of 19 Great Waters recognized by the America's Great Waters Coalition.
The Brazos River, called the Rio de los Brazos de Dios by early Spanish explorers (translated as "The River of the Arms of God"), is the longest river in Texas and the 11th longest river in the United States at 2,060 km (1,280 mi) from its headwater source at the head of Blackwater Draw, Curry County, New Mexico to its mouth at the Gulf of Mexico with a 116,000 km2 (45,000 sq mi) drainage basin.
The Canadian River (Pawnee: Kícpahat ) is the longest tributary of the Arkansas River. It is about 906 miles (1,458 km) long, starting in Colorado and traveling through New Mexico, the Texas Panhandle, and Oklahoma.
The Canadian is sometimes referred to as the South Canadian River to differentiate it from the North Canadian River that flows into it.
The United States is a country in the Northern Hemisphere, Western Hemisphere, and the Eastern Hemisphere. It consists of forty-eight contiguous states in North America, Alaska, a peninsula which forms the northwestern most part of North America, and Hawaii, an archipelago in the Pacific Ocean. There are several United States territories in the Pacific and Caribbean. The term "United States", when used in the geographical sense, means the continental United States, Alaska, Hawaii, Puerto Rico, Guam, and the Virgin Islands of the United States. The country shares land borders with Canada and Mexico and maritime (water) borders with Russia, Cuba, and the Bahamas in addition to Canada and Mexico.
The geography of Texas is diverse and far reaching in scope. Occupying about 7% of the total water and land area of the U.S., it is the second largest state after Alaska, and is the southernmost part of the Great Plains, which end in the south against the folded Sierra Madre Oriental of Mexico. Texas is in the south-central part of the United States of America, and is considered to form part of the U.S. South and also part of the U.S. Southwest.
By residents, the state is generally divided into North Texas, East Texas, Central Texas, South Texas, West Texas (and sometimes the Panhandle), but according to the Texas Almanac, Texas has four major physical regions: Gulf Coastal Plains, Interior Lowlands, Great Plains, and Basin and Range Province. This has been cited as the difference between human geography and physical geography, although the fact that Texas was granted the prerogative to divide into as many as five U.S. states may be a historical motive for Texans defining their state as containing exactly five regions.