Pecatonica, IL has a population of 2,315 and is the 10,229th largest city in the United States. The population density is 1,793 per sq mi which is 686% higher than the Illinois average and 1879% higher than the national average. The median age in Pecatonica is 41 which is approximately 10% higher than the Illinois average of 37. In Pecatonica, 58% of the population over 15 years of age are married, 98% speak English and 0% speak Spanish. 84% of Pecatonica residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 1% were foreign born.