The palatial Congress Theater in Chicago knows how to throw a New Year’s Eve celebration. Last year, Girl Talk rang in 2010 to a packed house. This year, electronic heavyweights Pretty Lights and the Diplo / DJ Switch collaboration Major Lazer were called upon to soundtrack one of the night’s biggest parties. The DJs (and Lazer’s hype-man Skerrit Bwoy) kept things uptempo, blasting another sold-out crowd with deep bass, hip-hop beats, and turntable theatrics. Photographer Tracy Graham attended the show and captured these great photos.