Olney, IL has a population of 8,931 and is the 4,296th largest city in the United States. The population density is 1,246 per sq mi which is 447% higher than the Illinois average and 1276% higher than the national average. The median age in Olney is 42 which is approximately 11% higher than the Illinois average of 37. In Olney, 58% of the population over 15 years of age are married, 97% speak English and 1% speak Spanish. 76% of Olney residents were born in Illinois, 22% were born out of state, 0% were born outside of the United States and 2% were foreign born.