Tony Award-winning actor best known for originating the role of Moritz Stiefel in the Broadway production of Spring Awakening. His other stage credits include American Idiot and Jerusalem. He also starred as Jim Harper on the HBO series The Newsroom.
He acted as a child at the Delaware Children's Theatre, and his professional acting debut came on television as one of the supporting actors in Hallmark Channel's original movie The Flamingo Rising.
He starred as Johnny in the Green Day Broadway musical American Idiot, and as Lee in the Broadway production of Jerusalem. Also a musician, he played in numerous bands, including Old Springs Pike, What Now, and Annie's Autograph.
He was born Wilmington, Delaware, the youngest of three children born to folk musicians John and June Gallagher.
He appeared in a 2002 episode of Aaron Sorkin's The West Wing, and Sorkin brought him back to star in The Newsroom.