Most Sustainable City, 2008: Portland, Ore.

Portland, Ore., is the most sustainable of the 50 most-populous cities in the U.S., according to the SustainLane 2008 US City rankings.

According to SustainableCities Corp., the owner of the rankings, it is "the nation’s most complete report card on urban sustainability."

The rankings gauge how well factors like "public transit, renewable energy, local food, and development approaches are most likely to either limit or intensify the negative economic and environmental impacts of fossil fuel dependence."

It might surprise you to know that the nation's largest cities are among the highest-ranking ones. For example, San Francisco ranks #2 (not much of a surprise, actually), Chicago #4, and that symbol of urban congestion and crowding, New York, comes in at #5.

At the other end of the scale, sunny Mesa, Ariz. (2007 population: 452,933), brings up the rear at #50.

(Photo: Portland, Ore., by lilemgee a.k.a. Mary Goodwater.)