The authors describe their experiences teaching Sustainable Cities in North America, a course on both urban sociology and urban sustainability. This course brought students to Portland, Oregon, and Vancouver, British Columbia, and then compared those cities with Minneapolis, Minnesota, on various dimensions of urban sustainability. After connecting this course to existing sociological scholarship on teaching urban sociology and travel-study abroad, the authors describe their course "in action": what they did, why it was (and was not) "green," and an assessment of the course, including postcourse actions and institutional changes that the course inspired. The authors conclude with a call for more "green" sociology courses and travel-study abroad courses as innovative and exciting ways to teach sociology and to further the discipline's commitment to ethical environmental actions.