Louisiana (La Louisiane la lwizjan; La Luisiana) is a state in the Deep South and South Central regions of the United States. It is bordered by the state of Texas to the west, Arkansas to the north, Mississippi to the east, and the Gulf of Mexico to the south; a large part of its eastern boundary is demarcated by the Mississippi River. Of the 50 U.S. states, it ranks 20th in land area and the 25th in population, with roughly 4.6 million residents. Reflecting its French heritage, Louisiana is the only U.S. state with political subdivisions termed parishes, which are equivalent to counties, making it one of only two U.S. states not subdivided into counties (the other being Alaska and its boroughs). The state's capital is Baton Rouge, which has a population of roughly 227,000 people and its largest city is New Orleans, with a population of roughly 383,000 people.
Much of Louisiana's lands were formed from sediment washed down the Mississippi River, leaving enormous deltas and vast areas of coastal marsh and swamp. These contain a rich southern biota, including birds such as ibises and egrets, many species of tree frogs—such as the state recognized American green tree frog—and fish such as sturgeon and paddlefish. More elevated areas, particularly in the north, contain a wide variety of ecosystems such as tallgrass prairie, longleaf pine forest and wet savannas; these support an exceptionally large number of plant species, including many species of terrestrial orchids and carnivorous plants. Over half the state is forested.
Louisiana is strategically situated at the confluence of the Mississippi river system and the Gulf of Mexico. Its location and biodiversity attracted various indigenous groups thousands of years before Europeans arrived in the 17th century. Louisiana has eighteen Native American tribes—the most of any southern state—of which four are federally recognized and ten that are state recognized. The French claimed the territory in 1682, and it became the political, commercial, and population center of the larger colony of New France.