Poplar Grove, IL has a population of 4,728 and is the 6,705th largest city in the United States. The population density is 617 per sq mi which is 178% higher than the Illinois average and 581% higher than the national average. The median age in Poplar Grove is 34 which is approximately 8% lower than the Illinois average of 37. In Poplar Grove, 71% of the population over 15 years of age are married, 92% speak English and 2% speak Spanish. 69% of Poplar Grove residents were born in Illinois, 23% were born out of state, 1% were born outside of the United States and 7% were foreign born.