New Castle, KY has a population of 1,079 and is the 14,670th largest city in the United States. The population density is 2,633 per sq mi which is 2329% higher than the Kentucky average and 2806% higher than the national average. The median age in New Castle is 42 which is approximately 8% higher than the Kentucky average of 39. In New Castle, 63% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 89% of New Castle residents were born in Kentucky, 11% were born out of state, 0% were born outside of the United States and 0% were foreign born.