Part of Chicago's skyline turned dark tonight as the city took part in Earth Hour 2011.

To save power and support energy efficiency, lights were turned off at 8:30 p.m. at such landmarks as the Merchandise Mart, the Wrigley Building, the NBC tower and many other buildings large and small.

ComEd officials planned to flip the switch at the Merchandise Mart because the Chicago landmark is the nation's largest building with LEED certification, a measure that takes into account energy saving, water efficiency, carbon dioxide emissions and more to give buildings a score on the "green" scale.

Among the many buildings in the city and suburbs that pledged to go dark for one hour included Navy Pier,  Willis Tower, the Chicago Theater, Wrigley Field, and the Trump International Hotel and Towers, according to ComEd.

The utility also said that communities across the area are participating, including Batavia, Evanston, Glenview, Oak Lawn, Skokie, Vernon Hills and Warrenville.

Earth Hour started in 2007 in Sydney, Australia, when people in that city and country turned their lights off to make a statement against climate change.  The event took off around the globe after that, with the World Wildlife Federation organizing an effort to get some of the world’s most iconic structures to join with their communities to go dark for an hour. Last year, a record 128 countries and territories participated, the agency said.

chicagobreaking@tribune.com