1776 after independence from British rule, 1789 became a unified federal republic. After more than 200 years of development, the economic, political and military strength of the United States has surpassed that of its former suzerain and any other country. After the disintegration of the Soviet Union, the United States became the only superpower in the world.

1776 The American War of Independence declared independence from Britain. 1789 After the formulation of the American Constitution, the United States became a federal republic and the first modern democratic country in the world. Since the19th century, the United States has gradually developed from the first 13 states in the eastern part of the North American continent to S in the central and western regions, and the area of the United States is increasing day by day. At the same time, the United States also has many territories overseas. The two major events in American history are the Civil War (186 1- 1865) and the Great Depression (1930s).