The importance of Illinois in winning the Civil War can scarcely be overemphasized. The state was a leading supplier of corn. wheat, and livestock to the army and to the nation; and Chicago was the West's leading commercial and industrial center. The strategic location of Cairo soon established that city as the troop and supply staging area for the Western campaigns.

Illinois contributed more than food, war material, and transportation. It also supplied manpower. Abraham Lincoln's first call for troops brought a flood of volunteers to Springfield to sign up. Although the Illinois quota was only six regiments, the General Assembly authorized an initial 10. By the war's end, 259,052 Illinois soldiers would serve, including at least 1811 Negro troops. Of the total number, only 3538 had to be drafted, and only 55 bought their way out by paying a substitute (a provision of the draft law of the time). The state fielded 17 infantry regiments, two light artillery regiments, eight independent artillery batteries, and several special units.

Most of the troops mustered in at Camp Douglas in Chicago or Camp Butler in Springfield. Regiments represented ethnic, geographic, and cultural groups including the "First Scotch," the "Rock Island Rifles," the "Lead Mine Regiment," and the "Preacher's Regiment." Regiments were headed by the man who recruited them, and noncommissioned officers were elected by the men.

Illinois also provided many of the Union Army's top officers. By April, 1865, a total of 177 Illinois generals of all kinds had served at some time during the conflict; and the state boasted 53 brigadier generals, nine major generals, and one lieutenant general. Politics was important in obtaining commissions, for the army was being improvised as needed, and governors appointed many officers. Regardless of the selection process, some outstanding leaders emerged, including Stephen A. Hurlbut; Napolean Bonaparte Buford; W.H.L. Wallace; John A. Logan; John A. McClernand; Richard Oglesby; John M. Palmer; Benjamin H. Grierson; John Pope; Silas A. Smith; Michael Lawler; and the greatest general of the war, U.S. Grant.

The General Assembly appropriated $3,500,000 in 1861 to support the war effort, and raised the money by obtaining loans from Chicago and Springfield banks. Former Governor Wood served as quartermaster general until the federal government took over supplying troops in 1862.

The loyalty of President Lincoln's home state was crucial, and Democratic Presidential candidate Stephen A. Douglas, Southern Illinois Democrat John A. Logan, and Republican Civil War Gov. Richard Yates were all influential in gaining and maintaining support for the Union cause. Illinois supported the war materially, martially, and morally. The state did its fair share and more.