Mount Carroll, IL has a population of 1,565 and is the 12,450th largest city in the United States. The population density is 781 per sq mi which is 251% higher than the Illinois average and 762% higher than the national average. The median age in Mount Carroll is 50 which is approximately 33% higher than the Illinois average of 37. In Mount Carroll, 61% of the population over 15 years of age are married, 95% speak English and 2% speak Spanish. 74% of Mount Carroll residents were born in Illinois, 25% were born out of state, 1% were born outside of the United States and 1% were foreign born.