Kewanee, IL has a population of 12,755 and is the 3,257th largest city in the United States. The population density is 1,900 per sq mi which is 755% higher than the Illinois average and 1997% higher than the national average. The median age in Kewanee is 39 which is approximately 3% higher than the Illinois average of 37. In Kewanee, 57% of the population over 15 years of age are married, 88% speak English and 10% speak Spanish. 78% of Kewanee residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 7% were foreign born.