Louisville, CO has a population of 19,972 and is the 2,179th largest city in the United States. The population density is 2,504 per sq mi which is 4929% higher than the Colorado average and 2663% higher than the national average. The median age in Louisville is 42 which is approximately 16% higher than the Colorado average of 36. In Louisville, 65% of the population over 15 years of age are married, 87% speak English and 3% speak Spanish. 32% of Louisville residents were born in Colorado, 57% were born out of state, 2% were born outside of the United States and 9% were foreign born.