Statehood The 21st state Dec. 3, 1818 Captial Springfield State Motto State sovereignty, national union Origin of State Name Illinois is named for the Illini, a confederation of Native Americans from various tribes who lived in the region. State Nickname The Prairie State Much of Illinois consisted of prairie, a broad, open grassland, when Europeans first settled there. Interesting Facts Abraham Lincoln's first public office was as postmaster of New Salem, Illinois. The first nuclear chain reaction took place in Illinois at the University of Chicago in 1942. Inventors John Deere and Cyrus McCormick made their fortunes in Illinois by improving farm machinery.