During the American Civil War, Illinois ranked fourth in men who served (more than 250,000) in the Union Army, a figure surpassed by only New York, Pennsylvania, and Ohio. Beginning with President Abraham Lincoln's first call for troops and continuing throughout the war, Illinois mustered 150 infantry regiments, which were numbered from the 7th to the 156th regiments. Seventeen cavalry regiments were also gathered, as well as two light artillery regiments. The town of Cairo, at the southern tip of the state at the confluence of the Mississippi and Ohio Rivers, served as a strategically important supply base and training center for the Union army. For several months, both General Grant and Admiral Foote had headquarters in Cairo.