The United States of America, or simply the United States, is a federal constitutional republic comprised of 50 states one federal district. Most of country lies in the central region of North America, made up of 48 states and Washington, D.C., the capital’s federal district. Bathed by the Pacific and Athlantic Oceans, it borders Canada to the north and Mexico to the South. The state of Alaska is in the northwest of the continent, bordering Canada in the east and with Russia to the west, through the Bering Strait. The state of Hawaii is na archipelago in the Central Pacific. The country also has several other territories in the Caribbean and the Pacific Ocean. With 9.37 million km² of area and a population of more than 300 million inhabitants, the country is the fourth largest in contiguous area and the third in population. The United States is one of the most multicultural and ethnically diverse nations in the world, a product of Strong immigration from many countries. Its geography and climate systems are also extremely diverse, with deserts, plains, forests and mountains housing a wide variety of species.