what county is thornton colorado located in
Thornton, Colorado - Basic Facts. The City of Thornton is the 6th largest city in Colorado with a population of 129,988 as of July 1, 2016. Thornton ranks in the upper quartile for Population Density and Diversity Index when compared to the other cities, towns and Census Designated Places (CDPs) in Colorado. See peer rankings below. The primary coordinate point for Thornton is located at latitude 39.9194 and longitude -104.9428 in Adams County.