Hillsboro, IL has a population of 7,287 and is the 5,037th largest city in the United States. The population density is 1,112 per sq mi which is 400% higher than the Illinois average and 1128% higher than the national average. The median age in Hillsboro is 37 which is approximately 1% lower than the Illinois average of 37. In Hillsboro, 36% of the population over 15 years of age are married, 97% speak English and 3% speak Spanish. 76% of Hillsboro residents were born in Illinois, 22% were born out of state, 0% were born outside of the United States and 1% were foreign born.