Castine, ME has a population of 899 and is the 15,800th largest city in the United States. The population density is 583 per sq mi which is 1452% higher than the Maine average and 544% higher than the national average. The median age in Castine is 21 which is approximately 53% lower than the Maine average of 44. In Castine, 16% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 46% of Castine residents were born in Maine, 51% were born out of state, 0% were born outside of the United States and 3% were foreign born.