Mount Vernon, IL has a population of 14,880 and is the 2,853rd largest city in the United States. The population density is 1,017 per sq mi which is 358% higher than the Illinois average and 1023% higher than the national average. The median age in Mount Vernon is 39 which is approximately 5% higher than the Illinois average of 37. In Mount Vernon, 50% of the population over 15 years of age are married, 96% speak English and 1% speak Spanish. 75% of Mount Vernon residents were born in Illinois, 22% were born out of state, 1% were born outside of the United States and 2% were foreign born.