New Plymouth, ID has a population of 1,931 and is the 11,217th largest city in the United States. The population density is 2,808 per sq mi which is 14619% higher than the Idaho average and 3000% higher than the national average. The median age in New Plymouth is 35 which is approximately 3% lower than the Idaho average of 36. In New Plymouth, 53% of the population over 15 years of age are married, 91% speak English and 8% speak Spanish. 34% of New Plymouth residents were born in Idaho, 62% were born out of state, 0% were born outside of the United States and 4% were foreign born.