Manlius, IL has a population of 400 and is the 20,882nd largest city in the United States. The population density is 1,306 per sq mi which is 488% higher than the Illinois average and 1342% higher than the national average. The median age in Manlius is 41 which is approximately 9% higher than the Illinois average of 37. In Manlius, 55% of the population over 15 years of age are married, 97% speak English and 3% speak Spanish. 92% of Manlius residents were born in Illinois, 8% were born out of state, 0% were born outside of the United States and 1% were foreign born.