Founded in 2006 in San Francisco, the initial Eco Tuesday event attracted about 60 participants. Now groups of up to 200+ show up every month to network and learn. Currently, Eco Tuesday is on the fourth Tuesday of every month in 10 cities across the U.S., in cities from Los Angeles to Detroit. Founded in 2006 in San Francisco, the initial Eco Tuesday event attracted about 60 participants. Now groups of up to 200+ show up every month to network and learn. Currently, Eco Tuesday is on the fourth Tuesday of every month in 10 cities across the U.S., in cities from Los Angeles to Detroit.