Shelley, ID has a population of 4,372 and is the 7,040th largest city in the United States. The population density is 2,437 per sq mi which is 12671% higher than the Idaho average and 2589% higher than the national average. The median age in Shelley is 24 which is approximately 33% lower than the Idaho average of 36. In Shelley, 62% of the population over 15 years of age are married, 90% speak English and 7% speak Spanish. 73% of Shelley residents were born in Idaho, 23% were born out of state, 0% were born outside of the United States and 4% were foreign born.