Geneseo, IL has a population of 6,589 and is the 5,401st largest city in the United States. The population density is 1,421 per sq mi which is 539% higher than the Illinois average and 1468% higher than the national average. The median age in Geneseo is 41 which is approximately 9% higher than the Illinois average of 37. In Geneseo, 69% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 76% of Geneseo residents were born in Illinois, 22% were born out of state, 1% were born outside of the United States and 1% were foreign born.