Worked on the Senate campaigns of Chuck Schumer and Hillary Clinton and the presidential bids of Democrats Bill Bradley and Howard Dean.
In 1998 he worked as a volunteer and intern for the Senate campaign of Charles Schumer, which led to jobs with Hillary Clinton's 2000 Senate campaign, Bill Bradley's 2000 presidential campaign, and Howard Dean's 2004 presidential campaign.
Attended John Burroughs School, where he took drama classes taught by Jon Hamm and graduated in 1995.
Graduated from the Juilliard School's Lila Acheson Wallace American Playwrights Program where he received both the Lila Acheson Wallace Juilliard Playwriting Fellowship and the Lincoln Center Le Compte du Nuoy Award.
Graduated in from Columbia University with both a BA in History.
Father Henry Pack Willimon was a captain the United States Navy, he resigned his commission to become a lawyer. Mother Nancy was a housewife.
Graduated in 2003 from Columbia University School of the Arts with a MFA in Playwriting.
President of the Writers Guild of America, East since 2017.