Rock Falls, IA has a population of 150 and is the 25,655th largest city in the United States. The population density is 710 per sq mi which is 1199% higher than the Iowa average and 683% higher than the national average. The median age in Rock Falls is 46 which is approximately 21% higher than the Iowa average of 38. In Rock Falls, 77% of the population over 15 years of age are married, 99% speak English and 1% speak Spanish. 89% of Rock Falls residents were born in Iowa, 7% were born out of state, 0% were born outside of the United States and 3% were foreign born.