The United States of America is a federal republic composed of 50 states, of which all except one-Hawaii islands - are in mainland America. The United States of America, which covers the central part of North America, grew out of the British colonies that were established in North America in the first half of the 17th century.

USA's participation in the First World War and the victory of the Allies made it a world power. The end of the Second World War saw the emergence of USA as one of the super-powers of the world.

The Union originally comprised 13 states, to which seven were added subsequently. Thirty other states, which were formerly territories, were also admitted into the Union as full states, thus making up 50 states in all, apart from the District of Columbia. Each state has its own constitution. The State constitutions provide for a legislature of two Houses, (except Nebraska which has only one House) a Governor and a judicial system of its own. The state governments can deal with all matters which are not reserved for the federal legislature. The existing states of the Union with their capitals are: