Population Totals for the State of Colorado
Historical Census
Population totals for Colorado, counties & places, 1870 to 2000 are available here.
Historical Census data can also be obtained through the University of Virginia. This site presents data for the people and the economy of the U.S. for each state and county from 1790 to 1960.
You may obtain a list of municipalities, their dates of incorporation and county locations at the State Archives.