Hillsdale, IL has a population of 557 and is the 18,903rd largest city in the United States. The population density is 862 per sq mi which is 288% higher than the Illinois average and 852% higher than the national average. The median age in Hillsdale is 43 which is approximately 16% higher than the Illinois average of 37. In Hillsdale, 62% of the population over 15 years of age are married, 98% speak English and 0% speak Spanish. 73% of Hillsdale residents were born in Illinois, 25% were born out of state, 0% were born outside of the United States and 2% were foreign born.