Idaho Falls, ID has a population of 58,933 and is the 668th largest city in the United States. The population density is 2,541 per sq mi which is 13220% higher than the Idaho average and 2705% higher than the national average. The median age in Idaho Falls is 33 which is approximately 7% lower than the Idaho average of 36. In Idaho Falls, 58% of the population over 15 years of age are married, 88% speak English and 10% speak Spanish. 56% of Idaho Falls residents were born in Idaho, 38% were born out of state, 1% were born outside of the United States and 6% were foreign born.