It is a federal republic of 50 states which originated in a revolution which separated a group of British colonies from the British Crown. However, it achieved its current size only in the mid-20th century. The U.S. Constitution, drafted in 1787, established a federal system with a division of powers that remained unchanged since its inception. The USA is a very racially, ethnically and culturally rich area, with its population hailing from many parts of the world due to the large amount of immigration throughout its history. It is also the worldʼs greatest economic power in terms of GDP. The nation’s wealth is partly a reflection of its rich natural resources and agricultural potential.