It’s been 20 years since the gallery’s first-ever exhibition—a show of early work by Gilbert and George, in a space on West 57th Street. Twenty years later, the now-landmark gallery James Cohan celebrates its anniversary with an exhibition that includes every artist in its current program. Among the works commissioned for the occasion are vibrant collages by both Elias Sime and Fred Tomaselli. Meanwhile, the gallery has a new flagship location in Tribeca, at 48 Walker Street. —E.C.