During the American Civil War, over 250,000 Illinois men served in the Union Army, more than any other northern state except New York, Pennsylvania and Ohio. Beginning with President Lincoln's first call for troops and continuing throughout the war, Illinois mustered 150 infantry regiments, which were numbered from the 7th Illinois to the 156th Illinois. Seventeen cavalry regiments were also mustered, as well as two light artillery regiments.
Source: Illinois in the Civil War. Retrieved February 1, 2005.