Princeton, IL has a population of 7,741 and is the 4,820th largest city in the United States. The population density is 963 per sq mi which is 333% higher than the Illinois average and 963% higher than the national average. The median age in Princeton is 44 which is approximately 18% higher than the Illinois average of 37. In Princeton, 58% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 85% of Princeton residents were born in Illinois, 13% were born out of state, 0% were born outside of the United States and 2% were foreign born.