Brookfield, IL has a population of 18,966 and is the 2,300th largest city in the United States. The population density is 6,192 per sq mi which is 2685% higher than the Illinois average and 6734% higher than the national average. The median age in Brookfield is 39 which is approximately 5% higher than the Illinois average of 37. In Brookfield, 57% of the population over 15 years of age are married, 82% speak English and 11% speak Spanish. 79% of Brookfield residents were born in Illinois, 12% were born out of state, 0% were born outside of the United States and 8% were foreign born.