Chadwick, IL has a population of 581 and is the 18,628th largest city in the United States. The population density is 1,866 per sq mi which is 739% higher than the Illinois average and 1959% higher than the national average. The median age in Chadwick is 46 which is approximately 22% higher than the Illinois average of 37. In Chadwick, 64% of the population over 15 years of age are married, 99% speak English and 1% speak Spanish. 76% of Chadwick residents were born in Illinois, 23% were born out of state, 1% were born outside of the United States and 1% were foreign born.