Yorkville, IL has a population of 18,436 and is the 2,363rd largest city in the United States. The population density is 922 per sq mi which is 315% higher than the Illinois average and 918% higher than the national average. The median age in Yorkville is 32 which is approximately 14% lower than the Illinois average of 37. In Yorkville, 64% of the population over 15 years of age are married, 89% speak English and 4% speak Spanish. 75% of Yorkville residents were born in Illinois, 18% were born out of state, 1% were born outside of the United States and 6% were foreign born.