Auburn, IL has a population of 5,006 and is the 6,468th largest city in the United States. The population density is 1,212 per sq mi which is 445% higher than the Illinois average and 1238% higher than the national average. The median age in Auburn is 37 which is approximately 2% lower than the Illinois average of 37. In Auburn, 59% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 78% of Auburn residents were born in Illinois, 20% were born out of state, 1% were born outside of the United States and 1% were foreign born.