Macomb, IL has a population of 18,771 and is the 2,326th largest city in the United States. The population density is 1,723 per sq mi which is 675% higher than the Illinois average and 1802% higher than the national average. The median age in Macomb is 24 which is approximately 35% lower than the Illinois average of 37. In Macomb, 36% of the population over 15 years of age are married, 91% speak English and 3% speak Spanish. 73% of Macomb residents were born in Illinois, 21% were born out of state, 0% were born outside of the United States and 6% were foreign born.