Shortly after the Battle of Fort Sumter, President Lincoln called for 75,000 volunteers. They were to serve for three months. The state of Illinois put out a call to form units. Six companies came from St. Clair County. Madison County sent three companies. Montgomery county sent one company. All nine companies met at Springfield, Illinois on April 23, 1861. There they were formed into the 9th Regiment, Illinois volunteer infantry. There were rumors that the Confederates intended to invade at Cairo, Illinois. In response, orders were issued for the 9th Infantry to occupy Cairo. They arrived and set up camp on May 1, 1861.