Millstadt, IL has a population of 3,911 and is the 7,551st largest city in the United States. The population density is 1,228 per sq mi which is 438% higher than the Illinois average and 1255% higher than the national average. The median age in Millstadt is 38 which is approximately 2% higher than the Illinois average of 37. In Millstadt, 63% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 76% of Millstadt residents were born in Illinois, 24% were born out of state, 0% were born outside of the United States and 0% were foreign born.