Colorado, mountainous state in the western United States; 270,000 km2, 5.1 million residents (2011). The capital is Denver with 600,200 residents (2010). Joined the Union in 1876 as the 38th state. Nickname: The Centennial State. COUNTRYAAH.COM: Lists all counties and parishes of Colorado in alphabetical order. Covers county profile and biggest counties by population in […]