There are a lot of different ways to measure the relative "greenness" of a given city. 
 
 You can look the energy efficiency of its buildings, the average carbon footprint of its citizens or even the number or people who have "An Inconvenient Truth" in their Netflix queue. 
 
 The people behind event finding app Gravy, on the other hand, used a different measure in determining their list of the greenest cities in America--the number of "green-friendly" events happening in a given year. 
 
 Does a critical mass of self-congratulatory "awareness building" festivals necessarily translate into a city and its citizens making serious strides toward protecting the Earth? 
 
 Of course not. But looking at the overall number of events does yield a pretty good idea of a city's level of publicly stated commitment to environmentalism, which often results in action. So it's not exactly surprising that the cities sitting atop Gravy's list for hosting the most environmentally-themed events also tend to cluster near the top of rankings of greenest cities based on other metrics. 
 
 Check out this list of Gravy's five "Most Earth-Friendly Cities" that comes complete with a unique Earth Day activity for each city: 
 
 Most Earth-Friendly Cities ||||| Which cities show the most eco-friendly pride? In honor of Earth Day, T+L readers separate the composters from the posers to determine America’s greenest cities. 
 
 San Francisco has a nationwide reputation for sustainable dining, but that’s not enough for many of its restaurants, which go to extra lengths to demonstrate their green practices. 
 
 “I’ve been handed a two-page printout, detailing how a particular fish came to be on my table,” says Michael McColl, the Bay Area founder of Ecotourism-Newswire.com. 
 
 Such attention to detail helps explain how San Francisco secured its spot among the top 10 of America’s Greenest Cities, according to the Travel + Leisure community. As part of the annual America’s Favorite Cities survey, readers ranked 35 metropolitan areas on a variety of travel-friendly qualities, from hotels to local microbrews and good wireless coverage. 
 
 To determine the greenest cities, we tallied the results from three survey categories: cleanliness, pedestrian-friendliness and public transit, and great public parks, which offset that urban asphalt and improve air quality. The high-ranking cities support other green initiatives that benefit travelers as well as locals: in Denver, the Brown Palace Hotel uses water from its own artesian well. Minneapolis offers cheap, easy-access bike rentals. 
 
 Then there’s Portland, OR, rated America’s No. 1 greenest city, where every day feels like Earth Day. One fourth of the city is shaded by tree canopy, and the ground itself features 288 parks. The Heathman Hotel, near light-rail and streetcar stops, completed a green overhaul and now even recycles “gently used” soap and shampoos, having them treated before sending them to area shelters. 
 
 Other American cities, of course, are eco-friendly in ways that aren’t always readily obvious. In a Siemens 2011 study that measured CO2 emissions, land use, air quality, and environmental governance, San Francisco came out on top—the city currently recycles 78 percent of its waste—and New York City ranked in the top 3 for its efficient land use and mass transit. 
 
 The Big Apple, however, didn’t crack the top 20 with Travel + Leisure voters, who were perhaps distracted by a rude welcome or subway stations in need of a good scrubbing. To be fair, the survey is based on readers’ perceptions, which can be skewed, and may not take into account recent improvements like New York’s expanding bike lanes and the High Line, a former rail track converted into an extraordinary park. 
 
 So which did make the green grade with T+L’s community? Read on for America’s greenest cities—and share your opinions in the comments below.
– You can measure the green-friendliness of a city in many ways—like its average carbon footprint per citizen or the energy efficiency of buildings. But the event-finding app Gravy has decided to measure cities by the number of pro-environmental events each one hosts in a year, the Huffington Post reports. Is this an official barometer? Hardly, but it does reflect people's interest in the green movement. Here are the top five US cities, each with a unique Earth Day activity: Portland: Operation Clean Street San Francisco: Earth Day SF Boston: Earth Day Massive Spin Jam Austin: Annual Earth Day Festival Chicago: Chicago Earth Day 5K Click for more.