Cave-In-Rock, IL has a population of 378 and is the 21,186th largest city in the United States. The population density is 1,012 per sq mi which is 355% higher than the Illinois average and 1017% higher than the national average. The median age in Cave-In-Rock is 36 which is approximately 3% lower than the Illinois average of 37. In Cave-In-Rock, 48% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 76% of Cave-In-Rock residents were born in Illinois, 21% were born out of state, 3% were born outside of the United States and 0% were foreign born.