Prairie Grove, IL has a population of 1,704 and is the 11,958th largest city in the United States. The population density is 298 per sq mi which is 34% higher than the Illinois average and 229% higher than the national average. The median age in Prairie Grove is 46 which is approximately 22% higher than the Illinois average of 37. In Prairie Grove, 63% of the population over 15 years of age are married, 94% speak English and 1% speak Spanish. 68% of Prairie Grove residents were born in Illinois, 26% were born out of state, 1% were born outside of the United States and 6% were foreign born.