By looking at the maps of the United State where it is shown the distribution of the population in 1870 it is possible to see that in general both areas, the Northeast and the Southeast, show a significantly higher population density than the population density found in the West and the Midwest. With areas of population densities of 90 and over inhabitants per square mile in the Northeast and Southeast, contrasting with areas of population densities under 2 inhabitants per square mile in the east.
However, since according to the same map described above The mean center of population for the United States was located in southern Ohio, it could be possible to state that in 1870 the Northeast was more densely populated than the Southeast.