The Westward Expansion of the USA

In every census since 1790 the mean center of American population has moved westward. In 1790 the most populated cities in the U.S. were all on the East Coast. By the 2010 census seven of the ten largest cities were located in the Sun Belt region of the south and west.

Creating Data has released a nice visualization of how the United States population has spread westwards since 1790. The County Populations map shows county population density across the United States for each decade from 1790 to 2010.

If you click on a date button you can view an animation of the population data from the selected decade.


This animated cartogram takes another approach to visualizing US Population Trends Over The Last 220 Years. This map shows the size the of the population in every U.S. state for every decade since 1790. As the animated cartogram plays you can clearly see the general migration westward in the United States as the western states begin to bulge on the map.


Another neat visualization of the westward migration in the U.S. is this map from the US Census Bureau. This animated map shows where the mean center of the population has been for each U.S. census from 1790 to 2010.

The Mean Center of Population for the United States 1790 to 2010 shows how the mean center of population in the US has shifted westward in the last 220 years from Kent County, Maryland to Texas County, Missouri.


This westward shift in the mean center of the population is also evident in the largest populated cities in each U.S. census. Josh Mahar has created an interactive map showing the top 10 U.S. cities by population in every census since 1790.

Using the Historical Look At America's Largest Cities map you can view the top ten most populated cities in each decade. The map sidebar also shows the population for each of the top ten cities in each census. If you turn on the annotations you can also find out a little more about the changing populations in the mapped cities.