Walpole, NH has a population of 401 and is the 20,869th largest city in the United States. The population density is 329 per sq mi which is 133% higher than the New Hampshire average and 264% higher than the national average. The median age in Walpole is 63 which is approximately 48% higher than the New Hampshire average of 42. In Walpole, 61% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 15% of Walpole residents were born in New Hampshire, 76% were born out of state, 9% were born outside of the United States and 0% were foreign born.