Essex, IL has a population of 787 and is the 16,719th largest city in the United States. The population density is 338 per sq mi which is 52% higher than the Illinois average and 273% higher than the national average. The median age in Essex is 36 which is approximately 3% lower than the Illinois average of 37. In Essex, 70% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 86% of Essex residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 0% were foreign born.