Colorado has two of the nation's four "happiest places," including the "happiest" place in the U.S., according to National Geographic.

The magazine listed its "25 Happiest Places in the United States" this week, and Boulder ranked No. 1 and Fort Collins ranked No. 4.

"Bolstered by a sense of community, access to nature, sustainable urban development and preservation policies, and perhaps even that clean mountain air, Boulderites overwhelmingly feel 'active and productive every day,'" according to bestselling author Dan Buettner, who along with National Geographic and Gallup researchers teamed up to create a happiness index.

The index uses 15 metrics to determine the "happiness" of a place, such as physical, social, community, financial, and purpose well-being.

Read more at the Denver Business Journal: