Wimsatt was born in Chicago, attended the University of Chicago Laboratory Schools, Kenwood Academy, and attended Oberlin College. His father, William C. Wimsatt, is a philosophy of science professor at the University of Chicago. Wimsatt uses "Upski" as his middle name, but it is really the graffiti tag he used growing up in Chicago.

Wimsatt's first book was Bomb The Suburbs (1994), a collection of essays celebrating urban life and critiquing the suburban mindset. The essay "We Use Words Like Mackadocious", previously printed in The Source (May 1993), celebrated and critiqued the wigger subculture. Wimsatt released No More Prisons (1999), referencing urbanism and the prison-industrial complex, in conjunction with an underground hip-hop album on Raptivism Records. Along with editing the books Another World is Possible (2001) and Future 500: Youth Organizing and Activism in the United States (2003), Wimsatt co-edited How To Get Stupid White Men Out Of Office (2004), a collection of stories from youth organizers around the world who won or swung elections. His latest book is Please Don't Bomb The Suburbs (Akashic Books, 2010).

Wimsatt founded the League of Young Voters (2003) and co-founded the Generational Alliance (2005). As a philanthropic consultant, he coined the term "Cool Rich Kids" (1999) to refer to young progressive philanthropists associated with the organization Resource Generation. He has consulted for dozens of organizations including Rock The Vote, MoveOn.org, and Green For All. He is currently a Fellow at the Movement Strategy Center directing The Field 3.0 Project, a dialogue and documentation effort to drive innovation in field organizing. He also runs All Hands On Deck, to mobilize young voters in swing states.