“A Mexican immigrant who spent the last 30 years of his life in California mental hospitals, [Martín] Ramírez, who died in 1963, is considered by some critics to be one of the greatest artists of the 20th century. He never, however, profited from his success — nor, until recently, did any members of his family.” With Ramírez works about to go on view in a New York gallery and at the American Folk Art Museum, and with other pieces in the collection of the Guggenheim, legal wrangling over ownership continues.