Oak Grove, KY has a population of 7,487 and is the 4,940th largest city in the United States. The population density is 699 per sq mi which is 545% higher than the Kentucky average and 672% higher than the national average. The median age in Oak Grove is 24 which is approximately 38% lower than the Kentucky average of 39. In Oak Grove, 54% of the population over 15 years of age are married, 94% speak English and 4% speak Spanish. 32% of Oak Grove residents were born in Kentucky, 63% were born out of state, 1% were born outside of the United States and 4% were foreign born.