Colfax, IA has a population of 1,925 and is the 11,239th largest city in the United States. The population density is 815 per sq mi which is 1392% higher than the Iowa average and 799% higher than the national average. The median age in Colfax is 39 which is approximately 3% higher than the Iowa average of 38. In Colfax, 64% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 84% of Colfax residents were born in Iowa, 14% were born out of state, 2% were born outside of the United States and 1% were foreign born.