Millions of U.S. homes, 2,200 businesses such as Walgreens and 45 national landmarks including Seattle’s Space Needle will go dark for an hour Saturday night to draw attention to global warming.

Despite debate over the science of climate change, a record number of U.S. cities, states, and businesses have pledged to participate in this year’s Earth Hour, in which non-essential lights go off at 8:30 p.m. local time, according to organizers.

The World Wildlife Fund started Earth Hour in Sydney, Australia, in 2007. The annual event has taken off since then. Last year, the group says, 4,000 cities turned off lights in official buildings in 87 countries, including 318 U.S. cities. It estimates 80 million Americans participated.

This year, 30 states (up from eight last year) plan to flip the light switch in governors’ mansions and other public buildings. Among monuments and other landmarks taking part: the Empire State Building, the Golden Gate Bridge, the Las Vegas Strip, Niagara Falls and the Willis Tower, formerly the Sears Tower, in Chicago.

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