Manhattan, IL has a population of 7,405 and is the 4,975th largest city in the United States. The population density is 1,124 per sq mi which is 393% higher than the Illinois average and 1141% higher than the national average. The median age in Manhattan is 31 which is approximately 17% lower than the Illinois average of 37. In Manhattan, 64% of the population over 15 years of age are married, 96% speak English and 1% speak Spanish. 87% of Manhattan residents were born in Illinois, 10% were born out of state, 0% were born outside of the United States and 2% were foreign born.