Jon Hamm rounds out the cast for “Howl,” the indie feature about the obscenity trial centering on Allen Ginsberg’s famed poem.

Hamm will star as defense attorney Jake Ehrlich, whose life was the inspiration for the TV series “Perry Mason.”

Cast includes James Franco, Mary-Louise Parker, David Strathairn, Jeff Daniels, Bob Balaban, Treat Williams and Alessandro Nivola.

Project is lensing in Gotham, with Werc Werk Works producing and fully financing. Rob Epstein and Jeffrey Friedman of Telling Pictures are helming based on their own screenplay. Producers are Werc Werk Works CEO Elizabeth Redleaf and president Christine Walker; Gus Van Sant exec produces with Redleaf.