 The Marcus collections included significant works by Mexican artists Rufino Tamayo, David Alfaro Siqueiros, Diego Rivera, and Rivera's lesser-known friend and colleague Antonio Ruíz; the American sculptor Alexander Calder, and American painter Georgia O'Keeffe.Marcus was friends with Rivera and Tamayo – playing a major role in bringing one of Tamayo's murals to the Dallas Museum of Art – and one of the first board members of the O'Keeffe museum, which honored him at the time of his death with a paid notice in "The New York Times" that stated "Stanley's generous support, leadership, enthusiasm, friendship and keen artistic judgment were instrumental in the Museum's inception and success.We shall miss him greatly."