Montgomery, IL has a population of 19,055 and is the 2,285th largest city in the United States. The population density is 2,036 per sq mi which is 816% higher than the Illinois average and 2148% higher than the national average. The median age in Montgomery is 33 which is approximately 11% lower than the Illinois average of 37. In Montgomery, 59% of the population over 15 years of age are married, 75% speak English and 20% speak Spanish. 73% of Montgomery residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 13% were foreign born.