Sue Canterbury, a curator at the Dallas Museum of Art, was visiting a collector when she noticed a dramatic painting of a lighthouse. The brushwork seemed familiar, yet the composition was wholly original. “I’m standing across the room thinking, ‘Who is that?’” It was Ida O’Keeffe (1889-1961), once considered by her family to be more talented than her eldest sister, Georgia, one of the biggest names in 20th-century art. Ida reportedly grumbled that she’d be famous, too, if she had a Stieglitz. Alfred Stieglitz, the legendary photographer, was Georgia’s husband, patron and gallerist. Ida, by contrast, supported herself as a nurse and teacher, painting about 70 known canvases in her life. Canterbury’s rediscovery led to an extensive hunt for Ida’s work and a major exhibition that raises tantalizing questions about all the gifted women overlooked in an era when so few were given a chance. “Could she have been on the level of Georgia?” Canterbury asks. “That will have to remain unanswered.”