Arco, ID has a population of 1,018 and is the 15,046th largest city in the United States. The population density is 961 per sq mi which is 4957% higher than the Idaho average and 961% higher than the national average. The median age in Arco is 43 which is approximately 22% higher than the Idaho average of 35. In Arco, 51% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 52% of Arco residents were born in Idaho, 46% were born out of state, 1% were born outside of the United States and 1% were foreign born.