Deerfield, IL has a population of 18,686 and is the 2,338th largest city in the United States. The population density is 3,381 per sq mi which is 1421% higher than the Illinois average and 3632% higher than the national average. The median age in Deerfield is 44 which is approximately 17% higher than the Illinois average of 37. In Deerfield, 70% of the population over 15 years of age are married, 90% speak English and 3% speak Spanish. 68% of Deerfield residents were born in Illinois, 22% were born out of state, 1% were born outside of the United States and 9% were foreign born.