Newcastle, ME has a population of 625 and is the 18,177th largest city in the United States. The population density is 288 per sq mi which is 668% higher than the Maine average and 218% higher than the national average. The median age in Newcastle is 50 which is approximately 15% higher than the Maine average of 44. In Newcastle, 51% of the population over 15 years of age are married, 91% speak English and 1% speak Spanish. 43% of Newcastle residents were born in Maine, 51% were born out of state, 0% were born outside of the United States and 6% were foreign born.