Middleton, ID has a population of 6,416 and is the 5,514th largest city in the United States. The population density is 1,189 per sq mi which is 6131% higher than the Idaho average and 1212% higher than the national average. The median age in Middleton is 32 which is approximately 9% lower than the Idaho average of 36. In Middleton, 61% of the population over 15 years of age are married, 93% speak English and 5% speak Spanish. 54% of Middleton residents were born in Idaho, 43% were born out of state, 1% were born outside of the United States and 2% were foreign born.