At Hack City, hackers, concerned citizens and passionate observers converged for GreenBiz Group's three-day marathon aimed at developing applications (mobile and web-based) aiming to create efficiencies in the energy, building management and transportation sectors. The event took place at Code for America's San Francisco offices.

Get a greater sense of the hackathon's goals -- as well as the energy in the room -- by watching the video below produced by GreenBiz Group Executive Producer Samuel O. Smith and cinematographer Avery Hudson. Watch a video of the "Hack City Theme Song" by hackathon organizer and GreenBiz Group Web Producer Krys Freeman here. See a slideshow of Hack City here.

Photo of Hack City hackathon participants working by Goodwin Ogbuehi/GreenBiz Group.