Deer Grove, IL has a population of 39 and is the 28,400th largest city in the United States. The population density is 86 per sq mi which is 61% lower than the Illinois average and 5% lower than the national average. The median age in Deer Grove is 48 which is approximately 29% higher than the Illinois average of 37. In Deer Grove, 72% of the population over 15 years of age are married, 84% speak English and 0% speak Spanish. 67% of Deer Grove residents were born in Illinois, 23% were born out of state, 0% were born outside of the United States and 10% were foreign born.