DALLAS — The abstract painting of a lighthouse caught the eye of Dallas Museum of Art curator Sue Canterbury as she visited a private collector about five years ago. Struggling to identify the artist, she walked up to the work and looked at the signature. "I was like everyone else is to whom I speak about her now: 'Ida O'Keeffe?'"

Canterbury has spent the ensuing years tracking down the works of renowned artist Georgia O'Keeffe's sister Ida Ten Eyck O'Keeffe. When the exhibit "Ida O'Keeffe: Escaping Georgia's Shadow" opens on Nov. 18 at the Dallas museum it will feature about 30 of her works, and Canterbury still hopes to find more, including the one painting from a series of seven depicting a Cape Cod lighthouse that she hasn't yet located.

"It's been really difficult and there are works that I have really great pictures of them, but they've disappeared into collections somewhere and not even dealers can help me find where they are," Canterbury said.

Serendipity has played a role in her search. Jewelry designer Neil Lane got in touch with Canterbury after seeing information about her quest online. He had one of the lighthouse paintings, which he had bought some 25 years ago at a Los Angeles-area flea market. "It was beautiful and well done," Lane said, adding, "It has substance. It wasn't just an amateur."

Ida O'Keeffe painted the lighthouse series in 1933 and kept them with her until her death in 1961 at the age of 71. Canterbury believes the one lighthouse painting she hasn't been able to find — the first and most realistic of the abstract series — is probably in California.

After Ida O'Keeffe died in Whittier, near Los Angeles, her artwork went to her sister Claudia O'Keeffe, who lived nearby. After Claudia O'Keeffe died in 1984, Ida O'Keeffe's works began to trickle out into the public.

One notable difference between Georgia and Ida O'Keeffe was the time they were able to spend focused on their art. Georgia benefited from the support of the man who eventually became her husband, the acclaimed photographer and gallery owner Alfred Stieglitz.

Ida O'Keeffe, a professionally trained artist who got a master's in fine arts from Columbia University, squeezed in creating art and exhibiting it while working a series of jobs that included teaching art at schools and working as a nurse.

"There were no saviors for Ida," Canterbury said. "Accounts say Ida said to Georgia on more than one occasion: 'I'd be famous, too, if I'd have had a Stieglitz,' which drove Georgia nuts."

The sisters grew apart after Georgia O'Keeffe, one of America's most successful artists by the mid-1920s, didn't support her sister's artistic endeavors. "She didn't want anyone riding on her name — the other O'Keeffe sister — and that's the way all the dealers were positioning it," Canterbury said.

Barbara Buhler Lynes, a leading Georgia O'Keeffe scholar and former curator of the Georgia O'Keeffe Museum in Santa Fe, New Mexico, said Georgia O'Keeffe discouraged other family members from trying to become artists.

"It was very difficult for a woman to be recognized as an important artist," Lynes said. "To have two in the same family vying for the same position, on some level you can see it as her rejecting her sister; on the other hand you could see it as a very practical thing."

Lynes said that while, for her, Ida O'Keeffe's work isn't as "powerful" as Georgia O'Keeffe's, it "has a sense of presence" and is "recognizably interesting."

"Some of (Georgia) O'Keeffe's are better than others and some of Ida's are better than others," Lynes said, "Some of Ida O'Keeffe's works are really quite great. I mean they're really quite wonderful."