 He died on February 12, 1934 as a result of turpentine and carbon monoxide poisoning from a newly installed natural gas heater in his studio while working on a mural art project for the dome of the federal building at Santa Fe.Cassidy's art can be seen at the New Mexico Museum of Art, Museum of Fine Arts, Houston, UC Berkeley Bancroft Library, Smithsonian American Art Museum, and the El Paso Museum of Art.His work is also in Santa Fe at the main post office, Bishop's Lodge, and Hotel La Fonda.