Illinois was the 21st state admitted to the United States of America, but today is the name of a region with a few scattered survivor communities.
With a population near 40,000 between 1300 and 1400 AD, the Mississippian-culture city of Cahokia, in what is now southern Illinois, was the largest city within the future United States until after 1790, when it was surpassed by New York City. Gradually Cahokia and the area were abandoned, and at the time of the American Revolution, only about 2,000 Native American hunters and a small number of French villagers inhabited the Illinois area. United States migrant settlers began arriving from Kentucky in the 1810s; Illinois achieved statehood in 1818. The future metropolis of Chicago was founded in the 1830s on the banks of the Chicago River, one of the few natural harbors on southern Lake Michigan. Railroads and John Deere's invention of the self-scouring steel plow made central Illinois' rich prairie into some of the world's most productive and valuable farmlands, attracting immigrant farmers from Germany and Sweden.
By 1900, the growth of industrial jobs in the northern cities and coal mining in the central and southern areas attracted immigrants from Eastern and Southern Europe. Its manufacturing made the state a major arsenal in both World wars. The Great Migration of African Americans from the rural South to Chicago formed a large and important community that created the city's famous jazz and blues cultures.
Illinois suffered several nuclear strikes on Doomsday. The large metropolis of Chicago received multiple strikes. Targets in and around the city included Fermilab and the Argonne National Laboratory. Several Chicago suburbs were destroyed either by their own strikes or due to their proximity to the Chicago strikes. These included Joliet, Aurora and Des Plaines. There was also devastation to the region from nuclear strikes in northwest Indiana. The death toll in the Chicago metro area was enormous.
Military targets included Chanute Air Force Base, Scott Air Force Base, Naval Air Station Glenview, and Naval Station Great Lakes. This also led to the destruction of the towns of Belleville, Rantoul, Glenview, and Waukegan-North Chicago.
Other cities that were attacked included the state capital of Springfield, Peoria, Decatur and Rockford. East St. Louis was also destroyed during the nuclear strike on St. Louis.
Making matters even worse was Illinois's heavy reliance on nuclear power. Three nuclear plants suffered meltdowns after the attacks, two on Doomsday itself due to their proximity to targets in Joliet and North Chicago, and one in the following weeks after technicians shut it down but lacked the means to control the reactor's decay heat. These three meltdowns covered large areas of Grundy, Lake, and LaSalle Counties with radioactive material even more persistent than the missile fallout. Additional plants near Springfield and Kankakee were under construction but had fuel present; these have begun to leak in the years since and have become hazardous sites as well. Only in the Quad Cities, far from any target, were things stable enough that the nuclear plant could be safely shut down and maintained.
With the destruction of the state government and no contact with the federal government, the state fell into anarchy. Towns close to major strikes, like Alton and Zion, collapsed quickly. Though not harmed by direct strikes, the general lawlessness created by the refugee problem, radiation and the collapse of the national infrastructure forced these towns to be abandoned as the population sought food and supplies elsewhere.
The interstates out of Chicago became choked with refugees, overwhelming the towns near them. For example, the town of Mattoon was overwhelmed after fighting with a large gang of refugees drove the citizens out of Mattoon out of their homes.
The communities along I-74 were somewhat more successful but only for a short while. In 1986, fighting broke out in the Champaign-Urbana area. Tension between the locals and the students at the University of Illinois led to riots and looting, turning the towns into a war zone. The twin cities of Bloomington and Normal were able to work together with the students of Illinois State University, but the refugee problem caused by strike at Peoria and the collapse at Champaign-Urbana caused the survivor government there to collapse in 1988. Today the area is controlled by several warlords who fight over the last remaining functional farms. One faction still calls itself the Illini Republic, and its major rival is "the Chinks." The core leadership is made up of refugees from Pekin, Illinois and they named their group after the infamous mascot of a local high school.
Remnants of the Illinois National Guard managed to reach safe areas in Kentucky while guarding several refugee convoys that attached themselves to the retreating units. All were eventually absorbed into the expanding Commonwealth of Kentucky. Many of these former survivors and their children are part of the first wave of Kentuckians who have established bases and outposts in southern Illinois.
A couple of organized survivor communities have risen in the former state. Along the banks of the Mississippi River is the the Quad Cities Alliance which encompasses territory in Illinois and Iowa. Also there is the small town of Charleston, which survived Doomsday thanks to an alliance between the local citizens and Eastern Illinois University. Smaller communities have also been discovered, including Vandalia, nestled in the lightly populated areas of the state. Bands of scavengers and nomads are also present, though they have begun to move out of the area as more explorers from the outside intrude on their territory. Kentucky controls most of southern Illinois.