According to the 2010 U.S. Census, the population of Illinois is 12,830,632. The estimated population in Illinois was 12,801,539 as of July 1, 2016 per the U.S. Census Bureau. Based on population, Illinois is the 5th largest U.S. state.
Minnesota is bigger than Illinois in size, and smaller in population. SIZE: Minnesota (#12 in size) is 86,943 square miles. Illinois (#25 in size) is 57,918 square miles. POPULATION: Illinois (#5 in population) has about 12,910,409 people. Minnesota (#21 in population) has about 5,266,214 people.