Mention Georgia O’Keeffe and most think of giant flowers. But the “mother of American Modernism” produced a far broader body of work. Her early charcoal drawings, first exhibited in 1916 and 1917, show her exploring organic form: the flick of hair to one side, the curve of a winding road, the sweep of a desert horizon. Now, 21 photogravures made between 1915 and 1963 highlight this formative period and O’Keeffe’s evolution into one of modernism’s defining figures. —Elena Clavarino