Description: This raster map shows the population density of the lower Mississippi Valley, by county, for the year 1990. Compared with the 1960 population map, this map shows that large areas of Missouri, Arkansas, and Louisiana are still sparsely populated. Many rural counties actually show population decreases. Most of the growth within the Mississippi Valley appears to be in the expansion of suburbia (urban sprawl) near the cities of St. Louis , New Orleans, Nashville, and Chicago. Source: U.S. Department of Commerce, Bureau of the Census.