Georgia O'Keeffe, 98, a painter whose rich abstractions and deceptively austere and brooding pictures of bones and flowers made her a leading force in modern American art, died yesterday at the St. Vincent Hospital in Santa Fe, N.M. The cause of death was not reported.

A child of the Midwest who was raised in Virginia and educated in New York and Chicago, Miss O'Keeffe lived in the Texas Panhandle from 1912 to 1918. Since 1929, she had spent most of her life in New Mexico, first in Taos and later at Abiquiu, a remote village in the high desert where she resided until last summer, when she moved to Santa Fe. It was from the American West, with its kaleidoscopic colors, harsh contrasts of light and shadow, and endless views of land and sky, that she drew inspiration for much of her work.

Some of her paintings of land or sky were immense abstract swirlings of color. Others were finely detailed depictions of skulls and bones bleached by the desert sun or microscopic studies of desert flowers. A major influence on her life and work was Alfred Stieglitz, the great photographer to whom she was married from 1924 until his death in 1946.

In 1977, Miss O'Keeffe received the Medal of Freedom, the nation's highest civilian honor. She also was one of the first to receive the National Medal of the Arts. In 1970, the Whitney Museum of American Art in New York put on a major retrospective show of her work. In December, one of her pictures, "White Rose, New Mexico," sold for $1,265,000 at auction at Sotheby's in New York.

"Her art is an individual one, expressing personal emotions and perceptions in a style that combines strength and crystalline clarity," wrote Lloyd Goodrich, who was director of the Whitney at the time of the O'Keeffe show.

The late Joshua Taylor, director of what was then the National Collection of Fine Arts, said in 1977 that Miss O'Keeffe was "a unique artist. She didn't found a school or generate followers, but she did develop a highly personal vision. She was also a very active part of an extremely important moment in American art -- the work that revolved around Stieglitz in New York. Some call it precisionism. That certainly describes the form, but not really the content. Precisionism implies the beauty of trim forms and clean shapes, but it doesn't convey the kind of poetry that O'Keeffe brought to the style."

J. Carter Brown, director of the National Gallery of Art, said at that time that Americans had long labored under "a national inferiority complex about art. When the Whitney did its retrospective , a lot of people's eyes were opened to the fact that there had geen a major talent very silently at work for all these years in New Mexico."

"I grew out of the grass," Miss O'Keeffe said in an interview with The Washington Post in 1977.

One of six children, she was born in a farm near Sun Prairie, Wis., on Nov. 15, 1887. Her parents were Francis Calixtus O'Keeffe, who was Irish, and Ida Totto O'Keeffe, who was of Dutch descent. She spent her early childhood there and in Madison, Wis. In 1902, the family moved to Williamsburg, and the future artist graduated from the Chatham Episcopal Institute, now Chatham Hall.

"I spoke differently from the other people," she said in 1977. "I knew door was door, I knew it wasn't doe . . . . I started out not having any friends at all, but I didn't pay any attention to it. They were still fighting the Civil War."

In 1905 and 1906, she attended the Art Institute of Chicago, and in 1907 and 1908 she was at the Art Students League in New York City. In the summer of 1912 she attended art classes taught by Alon Bement at the University of Virginia. She also studied with Arthur Dow, who had been a student of Paul Gaugin, and she embraced his theories of "filling a space in a beautiful way." In the autumn of 1912, she went to Amarillo, Tex., as supervisor of art in its public schools.

These are the formal steps Miss O'Keeffe took to become an artist and to make the acquaintance of the West. What set her on that road is less clear.

In the introduction of "Georgia O'Keeffe," a book about her paintings that appeared in 1976, she said:

"My first memory is of the brightness of light. Light all around. I was sitting among pillows on a quilt on the ground -- very large white pillows. The quilt was a cotton patchwork of two different kinds of material -- white with very red stars spotted over it quite close together, and black with a red and white flower on it. I was probably 8 or 9 months old. The quilt is partially a later memory, but I know it is the quilt I sat on that day . . . .

"The year I was finishing the eighth grade, I asked our washwoman's daughter what she was going to do when she grew up. She said she didn't know. I said very definitely -- as if I had thought it all out and my mind was made up -- 'I am going to be an artist.'

"I don't really know where I got my artist idea. The scraps of what I remember do not explain to me where it came from."

While in Texas, she decided to discard the constraints of much of the academic training that she had received and follow her own instincts. The result was a series of drawings which she sent to a friend in New York in 1916. They came to the attention of Stieglitz and he displayed them in his famous 291 Gallery.

The following year, Miss O'Keeffe went to the city to take back her work. Instead, Stieglitz persuaded her to allow him to put on a one-woman show. In 1924, she and the 61-year-old photographer were married.

"I was interested in what he did and he was interested in what I did," Miss O'Keeffe said in 1977. "That's the best kind of tie."

When she discovered New Mexico in 1929, Miss O'Keeffe spent part of every year there and Stieglitz would remain in New York. After his death, she spent three years settling his estate and then moved to the Southwest permanently.

In 1980, she agreed to have her house at Abiquiu taken over by the National Park Service after her death. In 1983, she asked that the agreement be rescinded because her neighbors in the village feared that they would be inundated by tourists.

In her later years Miss O'Keeffe also was involved in legal proceedings against a nephew who was making unauthorized lithographs of her work. But none of this seemed to disturb the serenity of her life. In her interview with The Post in 1977, which was given at Abiquiu, she said:

"I climb up that ladder onto the roof there and I can just stare out at the hills. I've been known to spend weeks up there, looking at how they've washed into new shapes. You can go up there and feel how good the world is."