Fort Knox, KY has a population of 9,226 and is the 4,181st largest city in the United States. The population density is 455 per sq mi which is 319% higher than the Kentucky average and 402% higher than the national average. The median age in Fort Knox is 24 which is approximately 38% lower than the Kentucky average of 39. In Fort Knox, 62% of the population over 15 years of age are married, 86% speak English and 9% speak Spanish. 8% of Fort Knox residents were born in Kentucky, 80% were born out of state, 6% were born outside of the United States and 6% were foreign born.