The imbalance in population between the two sections was roughly known by December of 1860, when the New York Times reported on the likely outcome of reapportionment, which would be in effect for the 1864 election. The newspaper story is on the internet, but it would be just clutter here, the static difference between the two sections was not the controlling factor. It was the analysis of the dynamic changes in the population from 1790 to 1860, summarized on the final page of the Preliminary Report on the 1860 census, provided here: https://www2.census.gov/library/publications/decennial/1860/preliminary-report/1860e-06.pdf?# that demonstrate the population growth of the seven state area, Ohio, Indiana, Illinois, Iowa, Michigan, Wisconsin, and Minnesota, had already established a momentum that was going to change the United States irrevocably. No military event could change that momentum. The population was already linked through Canada, back to Britain, Germany and Scandanavia. The 1864 report on the census, https://www2.census.gov/library/publications/decennial/1860/population/1860a-02.pdf?# even contains an analysis of the military age population of the United States at page xvii. The comments in Grant's memoirs, that the United States could have lost the military struggle, and continued to grow, were backed by substantial demographic evidence. In the various reports Superintendent Kennedy outlined the dynamic nature of the episode. A static map of the United States in 1860 is misleading. A dynamic analysis shows the effects of steam railroads and steamships.