During the Illinoian Stage of the Pleistocene, the Laurentide Ice Sheet covered about 85 percent of Illinois, including the Macon County area.The subsequent thaw of the region and retreat of the ice sheet left central Illinois with its present characteristic flat topography.[16] In its early years Macon County favored the Democratic Party, voting for it in every election through 1860.Republican Abraham Lincoln won the county in the 1864 election, and from then until the Great Depression Macon County became solidly Republican, only giving a narrow plurality to Woodrow Wilson in 1912 when the GOP was divided by Theodore Roosevelt's splinter–party run.The FDR-era New Deal saw the county become more amenable to the Democratic Party again due to its strong industrial base.