United States of America popularly referred to as the United States or as America, a federal republic on the continent of North America, consisting of 48 contiguous states and the two non-contiguous states of Alaska and Hawaii.As the nation developed, it expanded westward from small settlements along the Atlantic Coast, eventually including all the territory between the Atlantic and Pacific oceans across the middle of the North American continent, as well as two non-contiguous states and a number of territories.Throughout its history, the United States has faced struggles, both within the country between various ethnic, religious, political, and economic groups and with other nations.The history of the United States is the story of how the republic developed from colonial beginnings in the 16th century, when the first European explorers arrived, until modern times.Early American history began in the collision of European, West African, and Native American peoples in North America.The population diversified as immigrants arrived from all countries of the world.From its beginnings as a remote English colony, the United States has developed the largest economy in the world.The efforts to deal with and resolve these struggles have shaped the United States of America into the late 20th century.At the same time, the population and the economy of the United States grew and changed dramatically.