The United States of America, commonly known as the United States or America, is a federal republic consisting of 50 states, a federal district, five major self-governing territories, and various possessions. It is situated mostly in central North America, where it shares land borders with Canada to the north and Mexico to the south. The United States is a diverse country with a rich cultural heritage shaped by various immigrant groups over centuries. Its history spans from the early indigenous peoples to the colonial era, the formation of the nation through the American Revolution and Constitution, and its rise as a global superpower in the 20th and 21st centuries.