Which American city is the greenest depends on whom you ask. Every year dozens of publications and websites release their own assessments of which cities have the most environmentally conscious citizenry, the highest percentage of recycling or the lowest carbon footprint per capita. Portland, Oregon, Seattle and San Francisco are often top contenders, but some of the other leading choices may be a surprise.

The Daily Beast based a recent round-up of greenest U.S. cities on data collected by market research firm Experian Simmons, which has been tracking the greening of the nation for half a century. Researchers polled thousands of Americans to find out what percentage in different geographic regions think and act in an eco-conscious way versus what percentage do not, as well as what percentage make a conscious effort to recycle. The company also tracked the number of public transit trips per capita and the percentage of households that use solar heating by region. Honolulu, most likely by virtue of the fact that one percent of homes there utilize solar power, came out on top. New York, with more than double the amount of public transit ridership per capita than any other U.S. city, is #2, followed by San Francisco, Seattle and Boston.

Meanwhile, the website Ecosalon looked at similar types of data and drew different conclusions, finding San Francisco to be the greenest. Ecosalon was especially impressed by San Franciscans routinely voting for aggressive green programs (like banning plastic grocery bags and financing renewable energy sources for public facilities) and by the fact that the city diverts 70 percent of its waste, thanks to mandatory recycling and composting. To top it off, nearly half of all San Franciscans bike, walk or take public transit every day—and the city is on track to reduce its greenhouse gas emissions 20 percent below 1990 levels this year. Ecosalon ranks Portland, Oregon second, followed by Seattle, Chicago and New York.

In another ranking, Canadian research company Corporate Knights granted Portland, San Francisco and Seattle a three-way tie for America’s greenest city. Denver ranked #4 while Albuquerque, Charlotte (NC) and Oakland tied at fifth. “Unlike other city-sustainability rankings, this ranking focuses on the effort cities are making rather than on their results, which could take years to achieve,” reported Kent Portney, a Tufts University researcher who participated in the project. “In other words, this ranking is aspirational in nature.” He says that each city was awarded a point for undertaking one of 38 programs or policies listed by Corporate Knights, in categories such as smart growth, land-use planning, pollution prevention, etc.

And in yet another recent round-up, Mother Nature Network (MNN) declared Portland, Oregon—where 200 miles of dedicated bike lanes and legions of supporters of local and sustainable food sources rule—the nation’s greenest city. San Francisco, Boston, Oakland and Eugene (OR) round out MNN’s top five.

Regardless of which city is “greenest,” all U.S. cities are greening up every day because planners now realize the economic advantages of using less energy, recycling more and keeping air and water clean. We can all help by supporting municipal energy savings, recycling and composting programs, and community enhancement efforts. Who knows: If you keep it up, maybe your city will top one of next year’s lists.

Contacts: The Daily Beast, www.thedailybeast.com; Ecosalon, www.ecosalon.com; Corporate Knights, www.corporateknights.com; Mother Nature Network, www.mnn.com.

EarthTalk® is written and edited by Roddy Scheer and Doug Moss and is a registered trademark of E – The Environmental Magazine (www.emagazine.com). Send questions to: earthtalk@emagazine.com.