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The mean center of the United States population is determined by the United States Census Bureau from the results of each census. The Bureau defines it to be:
The concept of the center of population as used by the U.S. Census Bureau is that of a balance point. The center of population is the point at which an imaginary, weightless, rigid, and flat (no elevation effects) surface representation of the 50 states (or 48 conterminous states for calculations made prior to 1960) and the District of Columbia would balance if weights of identical size were placed on it so that each weight represented the location on one person. More specifically, this calculation is called the mean center of population.
After moving roughly 600 mi (966 km) west by south during the 19th century, during the 20th century the shift in the mean center of population was less pronounced, moving 324 mi (521 km) west and 101 mi (163 km) south. The southerly movement was much stronger during the second half of the 20th century; 79% of the southerly movement happened between 1950 and 2000.
Location info since 1790
The 20.7 mile shift projected for the 2010–2020 period would be the shortest centroid movement since the Great Depression intercensal period of 1930–1940.
Notes on the table data
- In the first census (1790) the mean population center was near Chestertown, Maryland.
- The mean population centers of 1820, 1830, 1840 and 1850 were in what is now West Virginia, given West Virginia's split from Virginia in 1863.
- Computation method used until 1950.
- Current computation method.
- The addition of Alaska and Hawaii to the union contributed to move the center about two miles (3 km) farther south and about ten miles (16 km) farther west in 1960.