After Grimshaw's return to Detroit, promoter
Russ Gibb hired him to perform light shows during rock performances at his new
Grande Ballroom. Grimshaw designed the first poster for the Grande Ballroom, for a show on October 7, 1966, featuring the MC5 and billed as "A Dance Concert in the San Francisco Style". Grimshaw was active in the anti-war movement and was a leading figure in the
White Panther Party, founded in 1968 by John Sinclair, his wife
Leni Sinclair and
Pun Plamondon. He was Minister of Art for the White Panther Party which modeled itself after the
Black Panther Party. His work appeared in many newspapers of the
underground press, including the
San Francisco Oracle, the
Berkeley Tribe, the
Fifth Estate and the
Ann Arbor Sun. Grimshaw had been convicted of displaying a "fifteen cent kite that had a dirty word lettered on it", and was sentenced to 15 days in jail and a $150.00 fine, but the court threw out his conviction and the Detroit ordinance, on the basis that it "unconstitutionally inhibits free speech". His political mentor John Sinclair was sent to prison on marijuana charges in 1969, and Grimshaw worked hard for his freedom. One of Grimshaw's most "memorable, iconic" posters promoted the
John Sinclair Freedom Rally, ==Later years and death==