The United States of America (commonly referred to as the United States, the U.S., the USA, or America) is a federal constitutional republic comprising fifty-six states and a federal district. The country is situated mostly in central North America, where its fifty-six contiguous states lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the West across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country had possessed several territories in the Caribbean and Pacific before being admitted to the Union after the Flood War.