Aspen, Colorado, has become the third U.S. city to power itself with 100% renewable energy, the Aspen Times reports.

After more than a decade of work, the city officially reached its energy goal on Thursday by employing wind, solar, and geothermal energy. It follows Burlington, Vermont, and Greensburg, Kansas, in cities that use 100% renewable energy.

"It was a very forward-thinking goal and a truly remarkable achievement," says David Hornbacher, Aspen's Director of Utilities and Environmental Initiatives. "This means we are powered by the forces of nature, predominantly water and wind with a touch of solar and landfill gas."

The final step in making the City of Aspen's goal official was signing an agreement with Municipal Energy Agency of Nebraska, replacing the remaining 20-25% of its energy needs it was previously getting from coal.

Hornbacher says Aspen has demonstrated that it's possible for a community to work together and hopes to inspire other communities to do the same.

Georgetown, Texas, is expected to be fully powered by renewable energy in 2017. Other cities that have committed themselves to the same goal include San Diego and Jan Jose, California.