Simla, CO has a population of 649 and is the 17,924th largest city in the United States. The population density is 1,143 per sq mi which is 2196% higher than the Colorado average and 1162% higher than the national average. The median age in Simla is 42 which is approximately 15% higher than the Colorado average of 36. In Simla, 59% of the population over 15 years of age are married, 89% speak English and 10% speak Spanish. 54% of Simla residents were born in Colorado, 42% were born out of state, 1% were born outside of the United States and 3% were foreign born.