Pontiac, IL has a population of 12,016 and is the 3,415th largest city in the United States. The population density is 1,468 per sq mi which is 560% higher than the Illinois average and 1520% higher than the national average. The median age in Pontiac is 39 which is approximately 4% higher than the Illinois average of 37. In Pontiac, 47% of the population over 15 years of age are married, 94% speak English and 4% speak Spanish. 83% of Pontiac residents were born in Illinois, 15% were born out of state, 0% were born outside of the United States and 1% were foreign born.