The United States of America is a constitutional federal republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait, and the state of Hawaii is an archipelago in the mid-Pacific. The United States also possesses several territories, or insular areas, scattered around the Caribbean and Pacific.

The ever-changing story of Americans, including their ancestry, their schooling, their relative wealth, and their mobility, is revealed by maps based on two centuries of census counts. Natural cataclysmic events that alter the landscape with sudden and terrible ferocity, like the Galveston hurricane of 1900 and the eruption of Mount St. Helens in 1980, are here. Longer term natural phenomena such as drought or glaciation, which affected America's earliest inhabitants, can be expressed effectively with maps. Human political developments, including exploration, territorial expansion, and elections results also greatly affect our ongoing history.