Fleming, CO has a population of 625 and is the 18,179th largest city in the United States. The population density is 1,201 per sq mi which is 2311% higher than the Colorado average and 1225% higher than the national average. The median age in Fleming is 37 which is approximately 1% higher than the Colorado average of 36. In Fleming, 64% of the population over 15 years of age are married, 98% speak English and 0% speak Spanish. 70% of Fleming residents were born in Colorado, 28% were born out of state, 0% were born outside of the United States and 2% were foreign born.