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:
After moving roughly  west by south during the 19th century, during the 20th century the shift in the mean center of population was less pronounced, moving west and 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.