Millbrook, NY has a population of 1,491 and is the 12,720th largest city in the United States. The population density is 772 per sq mi which is 115% higher than the New York average and 752% higher than the national average. The median age in Millbrook is 48 which is approximately 26% higher than the New York average of 38. In Millbrook, 57% of the population over 15 years of age are married, 91% speak English and 4% speak Spanish. 65% of Millbrook residents were born in New York, 27% were born out of state, 2% were born outside of the United States and 6% were foreign born.