Blackfoot, ID has a population of 11,878 and is the 3,442nd largest city in the United States. The population density is 2,007 per sq mi which is 10417% higher than the Idaho average and 2115% higher than the national average. The median age in Blackfoot is 31 which is approximately 15% lower than the Idaho average of 36. In Blackfoot, 62% of the population over 15 years of age are married, 83% speak English and 13% speak Spanish. 67% of Blackfoot residents were born in Idaho, 24% were born out of state, 1% were born outside of the United States and 8% were foreign born.